Alien Invaders in Your Yard!

Alien invaders are in our midst! They may not be blood-slurping killer carrots from outer space, but they are here all the same. In forests and meadows, wetlands and public parks, non-native invasive plants are on the march. Earthlings beware!

Each year, exotic invasive plants take over an area representing approximately 4,000 square miles, leading to billions of dollars in agricultural and forest product losses, and billions more in control costs. Your backyard may well represent a small but important skirmish in this chilling invasion scenario.

Invasive plants often dominate our personal landscapes. Often we inherit a property overrun with Japanese honeysuckle and English ivy, while at other times we ourselves are unwitting co-conspirators by purchasing and planting these exotic species, many of which represent the backbone of sales for garden centers, especially where groundcovers are concerned.

Of course, selecting these traditional invasive species is understandable enough. Non-native plants are generally inexpensive, readily available, and easy to maintain; after all, they really do grow and spread like weeds. And that’s just the problem! Or at least a part of the problem.

Non-native invaders damage our environment in numerous ways. The green scourge of kudzu in the Southeast has effectively conquered seven million acres of forest at a loss of 50 million dollars, and is now romping through wooded areas up and down the East Coast (and beyond). It smothers trees up to 100 feet tall, and overwhelms the natural landscape, much like multiflora rose, Asian wisteria, porcelainberry, and sharp-barbed mile-a-minute vine.

But there is an even more insidious side to this invasion. Exotic species also successfully (and insidiously) out-compete and replace native plants like horticultural body snatchers. This loss of native plants represents an overall loss of habitat and food sources for native wildlife. Consider the impact of the Bradford pear and its overuse as a street and landscape tree. Unlike a native ornamental tree, such as a viburnum or red chokeberry, which can provide food for dozens of bird species, the brittle Bradford pear attracts only European starlings, a winged plague in their own right, which help carry the invader's seeds far and wide in an example of sinister symbiosis.

English ivy is another example. It displaces native ground covers, inevitably escapes into natural areas, and eventually mutates from ground cover to tree strangler. Even well-manicured ivy beds around the home are potential fifth-columnists, as the seeds produced by the vine are favored by non-native birds, like our pesky starlings, and distributed over a wide area far beyond your backyard.

Unfortunately, the invasion can never be completely halted. Once a non-native species is successfully introduced, it is almost impossible to eradicate it completely. However, we can strike an effective blow for biodiversity in several important ways. First, know your enemy.

Find out more about which species are invasive, and NEVER consider purchasing or planting them. Besides those already mentioned, it is disappointing to note that a number of other vicious invaders are still sold as landscape ornamentals, including porcelainberry, Oriental bittersweet, and Japanese honeysuckle. Also invasive are popular groundcover standards like periwinkle and bugleweed (ajuga).

And, to aggravate the problem, mail order and Internet shopping has encouraged homeowners to buy species which should not be planted locally, or otherwise offer false claims about a specific variety being non-invasive. For example, horticultural writer Kathleen Fisher notes that gardeners in the Washington metropolitan area continue to plant purple loosestrife, an unstoppable invader of wetlands, perhaps due to an erroneous newspaper article touting a sterile cultivar. Not true. Keep away from this marauder and plant gayfeather (Liatris) instead.

Next, seek sensible alternatives. Most of the desirable characteristics sought in exotic species can be found in native plants. Substitute native ferns, golden ragwort, green-and-gold, native ginger, or Allegheny spurge for invasive ground-covers. Or, at least, select a non-invasive ground cover, such as pachysandra or sweet woodruff.

Invasive and almost clichéd hedges and foundation plantings like burning bush euonymus and Japanese barberry are more handsomely replaced with avian favorites such as winterberry, beautyberry, or inkberry. Privacy plantings like Leyland cyprus and the double threat of autumn and Russian olive can be replaced with American holly or eastern red cedar. Exotic species are very often easily identified by their common names: Japanese honeysuckle, Norway maple, Asian wisteria, Chinese bittersweet — and they are just as easily replaced by their native American counterparts, all of which are better suited to our bioregion, and more suitable for our resident wildlife.

Lastly, take up arms against the invaders. It is not going to be an easy fight. Ivy and honeysuckle will need to be cut, yanked, and grubbed up from the soil. And the fight will not be won overnight. Eradicating the most aggressive vines and ground covers will require constant vigilance and patience. Addressing larger plants, like shrubs and ornamental trees, will require some soul searching. It is never emotionally easy to cut down a tree, with the exception of a Bradford pear, which has probably lost half of its branches already. Moreover, a significant financial investment has often been made in these plantings. Perhaps the best solution in these cases is to defuse some of the alien invasion by expanding your current landscaping plan to include numerous native planting areas.

Copyright 2009, Joseph M. Keyser


Invasive Alien Species

Trees

Catalpa Catalpa spp.
Empress Tree Paulownia tomentosa
Norway Maple Acer platanoides
Sweet Cherry, Bird Cherry Prunus avium
Tree of Heaven Ailanthus altissima
White Mulberry Morus alba
White Poplar Populus alba
White Spruce Picea glauca

Vines

Cinnamon Vine Dioscorea oppositifolia
Climbing Euonymus Euonymus fortunei
English Ivy Hedera helix
Japanese Honeysuckle Lonicera japonica
Kudzu* Pueraria lobata
Mile-a-minute Polygonum perfoliatum
Oriental Bittersweet Celastrus orbiculatus
Periwinkle Vinca minor
Porcelain Berry Ampelopsis brevipedunculata
Wisteria Wisteria floribunda, W. sinensis

Herbaceous Plants

Beefsteak Mint Perilla frutescens
Bull Thistle* Cirsium vulgare
Canada Thistle* Cirsium arvense
Common Daylily Hemerocallis fulva
Creeping Bugleweed Ajuga reptans
Creeping Lilyturf Liriope spicata
Crown-vetch Coronilla varia
Eulalia (ornamental grass) Miscanthus sinensis
Garlic Mustard Alliaria petiolata (A. officinalis)
Giant Chickweed Myosoton aquaticum
Giant Knotweed Polygonum sachalinense
Ground Ivy Glechoma hederacea
Henbit Lamium amplexicaule
Indian Strawberry Duchesnea indica
Japanese Knotweed Polygonum cuspidatum
Japanese Stiltgrass Microstegium vimineum
Johnsongrass* Sorghum halepense
Lesser Celandine Ranunculus ficaria
Moneywort Lysimachia nummularia
Mugwort Artemisia vulgaris
Musk Thistle* Carduus nutans
Nodding Star of Bethlehem Ornithogalum umbellatum
Plumeless Thistle* Carduus acanthoides
Purple Dead Nettle Lamium purpureum
Purple Loosestrife Lythrum salicaria
Reed Canary Grass Phalaris arundinacea
Shattercane Sorghum bicolor
Spotted Knapweed Centaurea maculosa
Star of Bethlehem Ornithogalum nutans
Tall Fescue, K31 Fescue Festuca elatior
Wild Garlic* Allium vineale

*Regulated by state or federal law.

Creating a Jardin d’amour

For the poets of antiquity, through medieval and early modern troubadours, fragrant gardens and seductive bowers have been honored as the perfect setting for trysts and the exchange of lovers’ vows. So why not create your own romantic retreat in which to idle away time with your soul mate?

Romance, of course, begs for an intimate setting. Your lawn may be fine for croquet, but it will never replace the atmosphere of a secluded woodland dell, with or without frolicking nymphs. Fortunately, there are numerous inexpensive ways to transform an unused corner of your yard into an amorous setting.

One of the easiest and quickest options is to build or purchase a trellis, pergola, or arbor. Many specialty garden centers and upscale home improvement stores feature attractive structures fabricated from wrought-iron, copper, zinc, cedar, and redwood, most for less than several hundred dollars. An even wider variety can be found through garden catalogs or the Internet.

With the structure in place, you can create your romantic bower by planting climbing roses or other suitable vines. Roses, of course, have a stronger association with love than any other flower, although they are not necessarily the easiest plants to manage. Most climbers will take two to three years to achieve their full blooming potential, and they will not provide a lush display beyond spring, for the most part.

To ensure privacy and color from the outset, you should consider interplanting roses with other climbing vines, such as the dazzling cultivars of ornamental clematis, native coral honeysuckle, or even annual vines like hyacinth bean, with its rich purple seed pods, or old-fashioned and reliable sweetpeas. Mind your color scheme and select your flowering vines to complement the color of your roses.

Of course, you need not plant roses at all. Use some of the vines already cited, and also consider intriguing gems like passionflower, if the name does not seem too cloying, climbing hydrangea, or even grapes, although grapes need more care and a stronger support than other vines.

Inside your private garden, you may want to add a simple bistro table and chairs, should you plan to enjoy a romantic picnic or late night champagne rendezvous. Or you might just carry out a moisture-proof picnic blanket and several oversized pillows to recline and dine.

Water is always a lovely feature, either for day or night. If electricity is available, there are scores of multi-tiered fountains, copper urns with sprays, and soothing tabletop fountains available, often for less than 100 dollars. For daytime use, consider some of the solar fountains gaining popularity. Naturally, you will want to keep your water clean and moving to avoid unwanted mosquito guests.

Fragrance is another important consideration. If you wish to supplement your arbor plantings, you can surround your lover’s garden with lemon-scented daylilies or lavender, or keep a rose theme going with some antique roses or fragrant modern roses. You can also add tender potted plants, such as the many species of jasmine, everblooming-gardenia, dwarf citrus trees, and so forth. As many of the most fragrant plants are tropical, you will need to move them indoors during colder weather.

If you are more interested in a garden for moonlit trysts, focus on plants and flowers whose white and silver blooms and foliage can reflect lunar light while wafting an air of aromatic sensuality. Among the best choices are fast-climbing moonflower, silver vine, virgin’s bower (our native clematis), common yarrow, santolina, and various artemisia species, in addition to many of the jasmines and gardenias already suggested. You might also think about hanging baskets or urns heavily planted and overflowing with annuals such as white lobelia, sweet alyssum, and cream-colored petunias.

For evening use, stock up on soft-glowing votive candles, lanterns and other luminaries. Even miniature white lights can be woven into your vines or draped lazily atop the arbor structure. Forget about using large, smoking garden torches; they are meant for luaus, not love.

Naturally, we have addressed only the quickest approach for establishing your Jardin de Roman. A longer-term project might actually establish a true secret garden, walled-round with fragrant hedges of Persian lilac or English boxwood, or native shrubs like American Cranberrybush, nannyberry, arrowwood viburnum, or Summersweet Clethra.

While such an enterprise would be much more expensive and labor intensive, it would provide a larger, permanent retreat which could only become more appealing over time, and would allow for the addition of classical elements like a lily pond, statuary, pathways for intimate strolling, exotic topiary, as well as the garden structures we have already contemplated, or a more elaborate pavilion or tea house. It is your budget, after all, and you just might want to transform your entire backyard into a garden of love.

Of course, for true romantics, perhaps nothing more is necessary than a secluded garden nook, a candle or two, a tender rhapsody playing in the background, and the clink of wine glasses. Or, as an eleventh century Omar Khayyam put it, “A loaf of bread, a jug of wine, and thou beneath the bough, were paradise enow.”

Copyright 2009, Joseph M. Keyser

Hanging Baskets: Gardening at Eye-Level

Hanging baskets have come a long way from the plastic potted geraniums traditionally sold outside supermarkets. Garden centers beckon with Old World styled wrought-iron cages or light and elegant moss-filled wire baskets, along with artisan-forged hooks and brackets. And trailing petunias must now compete with an entire aerial garden of colorful snapdragons and fragrant heliotropes, surrounded by a riot of verbena, trailing lantana, nasturtiums, and Italian bellflowers.

Choosing your style of hanging garden partially depends on location and desired effect. Don’t set your heart on an overflowing jewel box of dazzling plants if your heavily shaded entryway can only accommodate a single accent plant or hanging fern.

Remember the gardener’s mantra: the right plant (or plants) in the right place. And don’t forget about your budget! Plastic is obviously less expensive and generally less attractive than wrought-iron, but you can partially remedy the situation by selecting plants which will completely cover the pot itself. Even so, you may want to substitute a woven hanger or metal chain in lieu of the galvanized hook wired onto most plastic containers.

Another important consideration is whether the hanging basket will become part of your design. For some gardeners, the antiqued bronze hook and Renaissance-themed wire basket is as important a design element as the plants living inside it. Similarly, you might try to match your container to your home: perhaps your country cottage would look best with a series of rustic brushwood baskets hanging from the eaves.

And before you begin to pick out plants, you should also consider both the basket liner and soil mix. Plastic has the advantage of retaining moisture more effectively than wire baskets, and will last for years. But for some, nothing compares with the natural beauty of either baskets filled with moss or, more commonly, coir-fiber. Environmentally, some folks prefer the latter, made from recycled coco fibers, rather than sphagnum moss, which is sometimes mined from sensitive bog areas. Other choices include liners fabricated from jute or sisal fibers.

Fiber and moss liners look great – but they do tend to dry out quickly, a real problem if you tend to forget your sun-parched planters, or leave town for days-on-end. My friend Tony swears by lining the inside of his basket with sheets of newsprint to prevent water loss . Another option is capillary matting, sold by the roll and easily cut to fit inside your containers. These highly absorbent mats can store and release water to root systems for days. Manufacturers suggest that they might even reduce watering requirements by up to 80 percent.

Your planting mix should be customized for hanging baskets, being both lightweight and porous to provide good drainage and aeration, while yet retaining moisture. Some container mixes are actually soil-less, and blend together peat moss or sphagnum moss, sand, vermiculite and/or perlite, and often include slow-release fertilizers. To one of these mixes you might consider adding one of the water-absorbent gels produced from polymerized potassium. These crystals are touted to act as reservoirs for water, holding up to 200 times their weight in water. But be sure to keep your watering wand handy!

Before rushing out to fill your basket, remember that only a large container, generally 16 inches in diameter or more, can readily sustain a large and dramatic collection of plants. Do not overwhelm smaller baskets with a nursery cart full of plants: a very common failing, and one I admit to myself. Containers less than 14 inches in diameter should only host a handful of favorites, probably two or three of the same plant, although you might include some trailing foliage plants, like ivy or asparagus fern, to provide texture and visual contrast. Smaller pots might only support a single plant, so pick something exuberant and colorful, combining a long-blooming period with a cascading form, such as variegated ivy geraniums or trailing verbenas, like the aptly named ‘Babylon’ variety.

With larger containers, select a “portfolio” of plants with similar requirements for sun, moisture, and feeding. Your hanging basket is a community, and no one plant should dominate the others or exhaust all of the water and nutrients. Shady locations should get shade-loving plants; sunny sites, sun-lovers.

And think of your hanging garden as a living floral arrangement. Depending on your taste and personality, you might choose a harmonious grouping of plants, such as soothing lavender and purple, blended with vines and foliage of green and silver. Or you might like the energy of contrasting a variety of hot, bright colors bursting out in all directions, and uniting the red, orange, yellow, and white blooms with gold, grey, and green foliage plants, such as the variegated ivies and pineapple mint, or lacy leaves of artemisia.

Your arrangement should also favor blends of textures and growth habits, taller geraniums and salvia, mounding petunias, annual vincas, begonias, and cascading multi-hued million bells, bluish-purple scaevola, or tried-and-true trailing lobelia and sweet alyssum.

For planning purposes, try to develop a shopping list in advance, organized into “planting zones” for your container. You will want an upright, compact, and colorful plant for the center of your container, and up to five or seven similar – not overpowering -- plants to fill the remaining top of the basket. Around the edge, plan on several plants to flow over the rim, filling the area between the top of the basket and the bottom, and several more trailing plants or vines to provide a fluid verticality to the whole. Either select personal favorites for your list, or consult with one of the skilled horticulturists at your favorite garden center.

Copyright 2009, Joseph M. Keyser

Smart Solutions for Steep, Sunny Slopes

A steep, sunny slope in your landscape can be a real challenge, especially if you’re trying to manage that area as a lawn. The slope itself makes mowing difficult -- if not outright dangerous -- and it is difficult to keep the turf green, as most water simply flows downhill, leaving the hillsides brown and barren. A proper solution should really turn this landscaping liability into an attractive asset.

There are a number of suitable solutions, but most are fairly expensive, such as designing and installing retaining walls, along with extensive replanting. Moreover, if the angle of your slope exceeds 20 degrees, you may need to engage a soils engineer or landscape architect. There might even be heavy equipment in your future. Ka-ching!

A simpler fix, ideal for the do-it-yourselfer, would simply call for replacing turf grass with a low maintenance ground cover. Keep in mind that many of the most popular ground covers are actually invasive weeds, and can often create management headaches in their own right. These include Five-leaf Akebia, Japanese Barberry, Crown Vetch, Wintercreeper (Euonymus fortunei), and English Ivy, which can often bake in full sun. Moreover, the “wild” nature of such plants makes mulching difficult, and can lead to even more weeds taking hold. So much for low maintenance!

For my money – or yours – one of the best solutions is an evergreen groundcover: something with an obedient and predictable growth habit, and an attractive year-round appearance. Think juniper.

There are literally scores of procumbent juniper species, and similar conifers, which will happily bask in the hottest sun, stretching across your hillside over the course of several years, all providing excellent erosion control and weed suppression, especially when combined with diligent annual mulching, and saving you the need to combine mowing with mountaineering. And these hardy plants are almost always drought-tolerant, helping to conserve water, while requiring no fertilizing.

Among the most common and popular junipers used as groundcovers are the creeping junipers (Juniperus horizontalis), slow to medium-growing shrubs, which form dense, aromatic mats between 12 and 18 inches in height, extending trailing branches from four to eight feet across, depending on the cultivar. Most feature either soft or prickly scale-like bluish-green foliage, which often “bronzes” once hit by cold winter temperatures. But don’t worry, they will “green up” again in the spring as air and soil temperatures warm up.

Blue Rug or ‘Wiltoni’ is probably the most popular juniper sold. It hugs the ground at four to six inches, and provides coverage up to eight feet in diameter. Blue Rug is drought-tolerant and thrives in conditions ranging from coastal Maine to the mountains of Georgia.

Other popular cultivars offer a Mardi Gras parade of colors and shades, from gold to green to purple, in a range of heights. Favorites include ‘Bar Harbor,’ which is similar to Blue Rug, although more colorful in winter, the bright green ‘Emerald Spreader,’ four-to-six inch tall ‘Prince of Wales,’ gold-variegated ‘Mother Lode,’ and ‘Pancake,’ lowest of the low at two-to-three inches.

‘Blue Star’(J. squamata) is a taller, different species, featuring cool blue foliage, and a pyramidal growth habit. This selection will generally stay below two feet in height, but can reach three feet, with only a two to four foot spread. It would be especially useful under a retaining wall for terraces, or against a rock outcropping.

Not all junipers are groundcovers: some are actually full-grown trees, like our native Eastern Red Cedar, which reaches an impressive 30 feet. Others tend to be shrubs, useful as hedges, such as the Chinese Junipers (J. chinensis), which reach about six feet in height, although some can become small trees up to 20 feet. One notable exception is Sargent Juniper, a cultivar that hovers at about 18 to 24 inches with an eight to ten foot spread. Many landscapers turned off by a juniper’s tendency to turn bronze in winter prefer Sargent, as it keeps its grayish-blue color year-round.

Dwarf Japanese Garden Juniper (J. procumbens ‘Nana’), provides bluish-green foliage which turns a stunning purple-bronze in late fall and winter. Horticulturist Mitch Baker (my go-to guy) at American Plant in Bethesda, Maryland is enthusiastic about ‘Nana’s’ spray-like mounding habit, which provides an exciting departure from the flat mat-like appearance of many other species, and allowing for a level of dimension to your hillside.

Mitch also noted options beyond junipers, such as the confusingly-named Siberian Juniper (Microbiata decussata), which is also called either Russian Arborvitae or Siberian Carpet Cypress, due to the shape of its foliage. Siberian Juniper is fairly new on the market, but is quite versatile thanks to its tolerance for Siberian winters and partial (not full) shade, as well as average soil and dry conditions. This specimen’s feathery foliage stays within eight to 12 inches in height, with an above-average ten foot spread.

And “spread” is the name of the game with junipers and other ground covers. Obviously, the wider the area covered by the plant, the fewer plants you will need. Most junipers can be planted approximately six feet apart, although you should check – and do the math – before purchasing and planting. Larger container stock, about three gallons, will provide a vigorous root system, ideal for early season planting, and will get your hillside off to a fine start.

Costs can range from 15 to 35 dollars, depending on the cultivar, size, and source. Smaller containers will be less expensive, but might take years to fill in. Don’t make the mistake of buying a lot of smaller containers and planting them too close together to create a finished look. Overcrowding can lead to disease problems and might require substantial transplanting in just a few years. Remember, you want a low-maintenance landscape: plan and plant properly, according to your budget, and let time and patience do the rest.

Decide in advance if you want to address the entire hillside at once, or just tackle a portion at a time. For best results, smother the grass or weeds on the site with landscape fabric or cardboard and a three to six inch layer of shredded wood mulch. Shredded mulch will lock together in place, where nuggets or chips might be washed off. Be sure to stagger your planting holes so that plants can diffuse flow down the slope and prevent erosive gullies. Check your soil to see if it needs amending with compost – although most junipers are tolerant of relatively poor soils as long as they receive good drainage.

Copyright 2009, Joseph M. Keyser

Moon Gardens for Luminous Landscapes

For some people, gardening is a diurnal affair: watch them as they toil, sweat, plan, and plant with peppy bright colors resplendent in the sun. Yet for romantic souls, twilight stirs enchantment and a pure quiet beauty which only awakens with the fall of night. For the nocturnal gardener, a moon garden is a phosphorescent paradise, filled with shimmering silver foliage, the subtle glow of white blossoms, and the sultry, intoxicating fragrance of night-blooming jasmines, stocks, and fantastic twining moonflowers.

Before the celestial magic begins, however, there are some earth-bound considerations. For starters, you probably don’t want to transform your entire landscape into a moon garden, although there are noteworthy precedents, such as Vita Sackville-West’s famous white gardens at Sissinghurst Castle in Britain.

Chances are you’ll prefer something smaller – perhaps just a border (or planter box!) beneath an open window. Be mindful that as many of the finest moon garden plants are both night-blooming and fragrant, you’ll want to keep both plants and aroma near at hand, where you can easily observe them opening. Why not even design your garden as an accompaniment to a patio or outdoor seating area?

With smaller specialty gardens, it often helps to create a single focal point. Consider using an old-fashioned gazing ball to reflect both the moonlight and moonlit blossoms. There are also newfangled solar-powered gazing balls, walkway luminaries, and hose guides, among other accessories, which can add a soft glow to your garden.

How about a lunar pool? Your centerpiece could be a small pond bordered with wooly thyme, lamb’s ears, aromatic santolina, and the fragrant creamy white flowers of petunias, along with white impatiens and vinca, and pure white salvia. The water itself, mirroring the night sky, might also host a fragrant, night-blooming water lily, such as Nymphaea ‘Trudy Slocum.’ And as sound becomes more audible in the relative quiet of night, you might enhance your sensory experience by adding a Japanese water flute or some similar dripping, bubbling, or gurgling feature.

Theme Gardens author Barbara Damrosch suggests using a lamppost as her focal point, with the added benefit of providing illumination on moonless nights. The post itself can become the support for any number of night-blooming vines. Or you might erect an arbor or trellis: the perfect home for our native virgin’s bower (Clematis virginiana), complete with clouds of white blossoms, feathery seeds, and a warm scent throughout the fall.

As for the plants: while the list is long for plants with silver-grey foliage or white flowers, your theme garden should concentrate on several key species -- beginning with moonflowers. How could you have a moon garden without it? Giant moonflower (Ipomea alba) is a fast-growing relative of morning glories, reaching up to twenty feet with sweetly fragrant six-inch trumpet-like blooms which unfurl at dusk – or on cloudy days. Grown as annuals in our area, they can be started from seed or purchased in small pots at garden centers for a dollar or two.

Angel’s Trumpet (Datura spp.), also called moonflower, is a focal point all by itself, with large, deep-fluted flowers opening up to eight inches long at twilight, and especially fragrant on warm-to-hot summer nights. The plant can reach three-to-four feet in height, with flowers projecting upward and outward. Often pure white, you might also look for pink, purple, and lavender varieties. From the nightshade family, the plant is extremely poisonous and should be avoided in gardens visited by children. Often grown as an annual, Patricia Manke at Behnke's Nursery in Potomac, Maryland notes that the plant can be dug up in late fall, allowing it to remain dormant in a garage or cool dark location, like caladiums or cannas, and replanted in spring.

Perhaps the most beloved evening aroma belongs to the rich and spicy, white-flowered and radiant members of the jasmine family, and sometimes to plants which only mimic the scent, such as night-flowering nicotiana, also called jasmine tobacco. Another impostor, night jasmine (Cestrum nocturnum) is not a jasmine at all! Rather, it’s a tropical shrub richly festooned with countless greenish-white blossoms coaxed open only at night. My smallish, pot-bound specimen easily broadcasts its unforgettable fragrance hundreds of yards through the night.

Other night-bloomers include the subtle sweetness of evening primrose (Oenothera speciosa), and night-scented stock (Matthiola bicornis), whose fragrance is strongly suggestive of nutmeg and vanilla. Four o’clocks (Mirabilis jalapa) bloom true to their name, and offer an interesting palette of colors (not white) ranging from dark purple and red to pink and yellow – and equally appealing to human noses and noshing by hummingbirds.

For 24-hour fragrance, you might include shrubs such as our native sweet pepperbush (Clethra alnifolia) and Virginia sweetspire (Itea virginica). Shrubs will also provide elements of structure to your garden, along with green leaves for a backdrop. Fothergilla is native to the southeast U.S., and well-worth selecting for its honey-scented flower clusters reminiscent of soft, creamy bottlebrushes.

Finally, any garden with a moon-theme ought to at least acknowledge the moon goddess Artemis (Diana to the Romans), if only by selecting some namesake plants from the genus Artemesia. Options include the very popular Artemesia ‘Silver Mound’ with feathery foliage, the almost too-common dusty miller, fern-like Roman wormwood (A. pontica) or true wormwood (Artemisia absynthium). For a royal touch, there are several taller white mugworts (A. ludoviciana) named ‘Silver King’ and ‘Silver Queen.’

Copyright 2009, Joseph M. Keyser

The Joys of High-Rise Horticulture

Whether you have a sliver of a balcony or a sun-drenched rooftop terrace, you can turn your aerial bit of the outdoors into a unique and personal garden in the clouds.

Too many people think that a small balcony has no better purpose than to sport a couple of cheap plastic chairs and a plastic table. But your slice of outdoor living can actually provide a dynamic living window on the world. Nondescript wrought-iron or aluminum railings can be set ablaze with stunning vines, decorative planters, hanging baskets, and maybe even a hummingbird feeder.

Imagine looking out your sliding glass doors through a tropical “window” created by hanging baskets with trailing vines in full bloom, along with attractive containers filled with sweet-scented vines twisting sensuously upward. Even if you overlook a parking lot – or other apartments – your view will be handsomely colored and enhanced by the foliage and plants which form a botanical picture window.

For example, a neighbor in Arlington routinely trains the tropical Mandevilla ‘Alice du Pont’ around the sides and front of her modest balcony. People routinely stop and stare up at her third-story flat, shielded from the southern sun by twining vines of large, glossy, deep-green leaves and enormous trumpet-shaped clusters of four to five inch-long hot-pink flowers, which bloom from spring through late summer and fall. Amazingly, her jungle canopy all sprouts from pots and baskets less than six inches in diameter.

Bear in mind that Mandevilla, like many of the tropical plants you may choose to employ, from ficus and ferns to dwarf orange trees, will need to overwinter with you indoors – or be replaced each year. Personally, I abhor letting perennials perish, and further welcome the touch of green in my indoor plantscape during the rainy, grey days of winter.

My own rather expansive rooftop oasis features unattractive wrought-iron and wooden railing. As a renter, I cannot change the materials – but I can certainly hide them. A large, 18-inch pot has comfortably housed a native wisteria vine for almost a dozen years. The vine covers more than 20 feet of railing and blooms profusely every spring. It is joined by 12-inch containers filled with trumpet vine and aromatic virgin’s bower, which cover much of the remaining railings, along with heirloom terracotta pots boasting a variety of fragrant jasmine varieties. Fortunately, only the jasmine plants are taken indoors in winter.

But there is much more to landscaping a roof or balcony than viney cover-ups. With proper exposure and good soil mixes, it is possible to grow most of your summer vegetables and herbs, from Ancho peppers to trellised zucchini, and all the tomatoes, lettuce, basil, and dill in between. Be sure to underplant your larger vegetables with parsley and tasty, brilliant-flowered nasturtiums.

Culinary herbs such as thyme, sage, oregano and rosemary, are readily grown in six to eight inch terracotta pots and set on a decorative étagère or tiered-plant stand. The neat organization will create an atmosphere of Provence, even if you can hear the Interstate in the distance.

There are some specific considerations for rooftop gardening which are best addressed before you begin planting. Watering can become a major chore if you cannot readily hook up a hose to an outdoor bib. I began my garden 25 or so years ago like Gunga Din, each day hauling buckets of water out to my garden. Soon after, I invested in a two dollar attachment for my bathroom faucet, screwed on a conventional garden hose, and have been watering hundreds of plants effortlessly, usually in less than 15 minutes.

Newcomers to atmospheric agriculture can now easily buy coil-style hoses for added convenience and simple storage. You will need the convenience because balcony and terrace gardens are almost exclusively container gardens, and containers, which are limited in their ability to retain soil moisture, need almost daily care.

Wind is another concern. Wind hastens evaporation, leaving plants thirsty, and can also make exposed areas terribly cold in winter, which can damage the roots and foliage of even tough perennials. During the winter, I have often moved my more cold-sensitive plants against a south-facing brick wall and huddle them together. I also try to remember to water them occasionally throughout the winter, especially during long periods of drought.

Also, be sure to adequately secure any taller specimens to prevent them from being blown over. While any number of ornamental conifers, lacey-leafed Japanese maples, crepe myrtle, and other small trees and shrubs thrive in fair-sized containers, their branches can easily catch a gust of wind, leading to a nasty tumble and damage to plant and pot alike.

For larger projects, such as a small water garden, pergola or permanent planter boxes, be sure to consult with an architect or structural engineer. Wet soil, evergreen shrubs, cast iron urns, small trees and the like, especially en masse, can create a significant load on your rooftop or balcony.

Fear not! After tackling the basics, the rest of your project is pure fun – or even fantasy. With an attractive arrangement of outdoor furniture, miniature white lights haphazardly draped through your shrubs or along your railing, and a burbling tabletop fountain, your terrace can become a vital outdoor living space, perfect for entertaining or just unwinding with a glass of wine.

You can use trellises set into planters, covered with passionflower vines or coral honeysuckle, to screen off your balcony from nosy neighbors or hide unsightly heat pumps. Similar trellis structures, or ornate pots with topiary shrubs, can also be organized in larger spaces to define special areas, such as a sun deck with lounge chairs, or an al fresco bar or dining room. With weatherproof speakers, you can even create a dance floor, unless the people downstairs object to midnight jitterbugging.

Additional structural elements like redwood arbors can support climbing roses, night-brightening moonflower vines, and transform a flat rooftop into an intimate personal landscape you may well prefer to indoor living. It has certainly worked such magic for two high-rise horticulturists, especially as we continue renting the same rooftop apartment overlooking Washington and dancing the nights away.

Copyright 2009, Joseph M. Keyser

Landscaping to Keep Cool - and Save Money!

Ah summer! The evening air is filled with the seductive smell of cookouts and steamed crab -- and the annoying hum of air conditioners. As the mercury keeps inching up into the nineties, the rising cost of keeping cool becomes more of an issue for many homeowners. Fortunately, there are landscaping solutions that can help save on energy costs without forcing you to break a sweat.

By properly positioning trees around our homes and reducing the amount of sunlight striking rooftops, walls, and windows, we can lower cooling costs by up to 25 percent. In fact, this type of natural cooling is much akin to using hats and sunscreen to protect delicate skin from harmful solar radiation.

Typically, the first step in an energy-efficient landscape is to plant a tree or trees on the south or southwest side of your home, where they can block the majority of sunlight, especially that striking your home in the mid- to late-afternoon. A couple of large trees, such as maples, oaks, and ash, will obviously produce the most shade, although smaller trees, such as dogwoods and serviceberry, can effectively screen the sides of a house.

Larger trees should be planted no closer than 20 feet from the house; smaller trees no closer than 15 feet. Among the fastest growing large shade trees are tulip poplars and sycamores, although both have somewhat weak branches and should never be planted where limbs can actually overhang the roof.

Deciduous trees, those that lose their leaves in winter, are more often planted than evergreens, as it generally desirable to allow the sun to provide passive solar heating in winter, at least for walls and windows. However, native evergreens, such as American holly, eastern red cedar, and eastern white pine, can also be used, depending on your overall landscaping theme.

Of course, if you plan to install photovoltaic cells or solar heat collectors on your roof, taking advantage of all that free solar energy, you will want to avoid shading the future location of your solar array. In this case, plant smaller growing trees that will primarily shade walls and windows.

If your property space cannot accommodate large trees, you can provide shading to walls and windows with small trees and shrubs like redbud, viburnum, deciduous azaleas, and inkberry holly. Be sure to keep shrubs about five feet away from the foundation to prevent problems with mold, mildew, and insect pests.

And while working around the foundation, why not use some evergreen shrubs like Mahonia and inkberry holly to shade your heat pump or air conditioner compressor. You will improve their efficiency, reduce some of the whining-whirring noise, and screen an otherwise unattractive bit of technology from view. Be careful that plants do not block airflow to and from the devices.

Another creative possibility is to use vines to shade wall areas and windows. Vines can either be trained to cover wall spaces, or can be attached to arbors and trellises. For example, Virginia creeper (or woodbine) can climb up the side of a masonry-covered wall without support, providing lush, attractive shade equaled only by its crimson-purple autumn foliage. Climbing hydrangea (Hydrangea anomala ssp. petiolaris) is also able to climb without support – or damage to building surfaces – and is a hardy and brilliant white-flowering specimen introduced from Asia in the 1860's.

Trellis structures can support a wide variety of vines and climbers, from showy roses to native favorites such as coral honeysuckle, crossvine, virgin’s bower, and American bittersweet. You can even take an edible landscaping approach and train pole beans or hyacinth beans to climb up string or wire supports.

It should be noted that shading fully exposed windows is more important than shading walls, most of which are fully insulated. For this reason, arbor structures built along the south side of a house can provide shade like a living awning, but with a great deal more beauty. You can train a host of interesting vines along the arbor, from edible kiwis and grapes, to ornamental hops and American wisteria.

Less involved window shading can be created with ordinary window boxes. Consider using some of the more colorful varieties of sweet potato vine, featuring dark purple, chartreuse, or tricolored leaves. These can be planted in your window box along with other colorful annuals and then trained to grow up and around the window frame. You will block out some of the sun’s heat while providing a dazzling window to the outdoors.

After addressing some of the direct sources of sunlight, think about the energy reflected from patios and walkways. Even the air temperature over grass is about ten degrees cooler than that over asphalt or other artificial surfaces. Simply shading these “hardscaped” areas can help appreciably, or you might want to reduce or replace concrete paths with natural, living materials, such as thyme lawns or mulched paths with herbal borders [see “Fragrant Pathway”]. Moreover, you can improve on the air conditioning benefit of lawns by replacing turf with clumps of native and ornamental grasses, perennial beds, and colorful groundcovers.

Keep in mind that landscaping to reduce energy costs can extend beyond merely shading rooftop and windows. According to national energy conservation expert Karen Anderson at the Alliance to Save Energy, “If it looks cool, it is cool.” Ms. Anderson is referring to the impression we have of a typical forest scene: green, serene, and lush with tall trees, ferns, and the leafy masses of smaller trees and shrubs. It always seems quite a bit cooler in such inviting environments because wooded areas really are cooler.

Trees and vegetation actually provide some chilling benefits through evaporative cooling, the transpiration of water through plant leaves. Research by the Lawrence Berkeley National Laboratory found that midday air temperatures were up to six degrees cooler in tree-shaded areas compared to treeless neighborhoods.

If you want to lower summer temperatures all around your home, try creating your own personal forest by grouping trees together in small groves and expanding green areas with ground covers and shrubs.

The more tree cover you establish, especially if it can help shade hot streets, sidewalks, and driveways, the cooler your immediate landscape will be. Naturally, if you work through a community association to get trees planted along streets and common areas, you can beautify your neighborhood, enhance overall property values, while keeping all of your homes more comfortable and energy efficient. Now that’s a cool idea!

Copyright 2009, Joseph M. Keyser

A Colonial Approach for Your Landscaping

A great many people seeking landscaping inspiration tend to overlook the actual style of their home. Certainly one of the most commonly found designs in our older, post-war communities is the so-called brick colonial, often complete with ye olde garage and driveway. These modern “colonials” typically feature an indeterminate landscape of lawns and azaleas rather than anything which might be considered truly Colonial, and perhaps better suited to the home and its setting.

Of course, there is a world of design opportunity and choice contained in the simple word “colonial,” ranging from Colonial Williamsburg and Mount Vernon, with formal garden areas which might be a tight squeeze in many urban and suburban areas, to the more rustic living history sites found at the National Colonial Farm in Accokeek, Maryland, or Claude Moore Colonial Farm in Virginia.

Chances are that most landscaping budgets will favor the latter approach, which is closer to the land and much more practical, although a simple seventeenth or eighteenth century working garden can certainly pick up an elegant element or two from gentrified living, such as a formal hedge or a tidy knot garden of aromatic herbs.

Many homeowners are inclined to consider boxwood hedges for foundation plantings and to define pathways, often in imitation of National Historic Trust properties. However, it should be pointed out that boxwood is a considerable investment, whether of time, where small containerized stock can take a decade or two to reach an appreciable size, or of money, where a grouping of larger shrubs can cost as much as a new car or two. Besides, Theme Gardens author Barbara Damrosch points out that the use of boxwood dates more to nineteenth century design than the colonial period itself. Historic accuracy could actually save you thousands of dollars, enough to buy some real antiques for your parlor.

As you consider design elements for your landscape, keep in mind that earlier gardens served a useful purpose and were not simply decorative. Your plant selections can and should reflect some of these practical considerations, prompting you to develop beds to provide tasty salad greens, culinary herbs, small fruits and berries, and so on.

The setting for your colonial garden is often dictated by the overall layout of your home. Small herb gardens can be built outside the back door to your kitchen. Larger, imaginative designs can take over your front yard, where a picket fence can enclose a somewhat formal pattern of walkways between garden plantings.

A garden for a sunny backyard might include a fence capable of excluding deer, which were as much of a problem for our colonial forebears as for modern suburban communities abutting wooded areas. You will find that some of the historic farm gardens nearby were constructed with tall fences of rough-hewn planks and timbers. Modern pre-made stockade fences will suffice, and can become the backdrop for raspberry canes, peas, and other climbing vines.

For craft-minded gardeners, consider erecting a thigh-high wattle fence, woven from twigs and small branches or straight sections of wild grapevine. These fences have graced gardens, and kept out rabbits, for over a millennium, and will now add a natural, historic feel to a lively salad garden brimming with chives, onions, garlic, and leeks.

Pathways through your garden or between beds can be built with elegant, recovered brick, crunchy pea gravel, or even crushed oyster shells, which were popular in some of the finer manor gardens. You can also fall back on a neatly manicured turf path or, easiest and least expensive of all, a simple mulched pathway. Select materials in keeping with your garden’s function. Is your garden designed as a showcase to set off your home? Or is it a working garden generating produce for your table and pantry?

The net effect of your garden may not rival the Governor’s Palace in Williamsburg, but artful design will match and enhance the traditional style of your home, while creating a flavorful and inspiring link to the past.

Copyright 2009, Joseph M. Keyser

Controlling Mosquitoes Around Home & Garden

Mosquitoes have buzzed around our planet for countless millions of years, long before the emergence of man and insect repellant. They have spread malaria across the globe, helped decimate isolated villages and have spoiled innumerable picnics and walks on the beach. At great cost — and to no avail — we have fought them with DDT, incense coils and backyard foggers.

Nowadays, mosquitoes are very much in the news. The reported incidence of malaria has quadrupled worldwide, while here in the U.S., the spread of West Nile Virus has mobilized public health officials and terrified residents. There even have been several futile efforts to use pesticide sprays to control adult mosquitoes.

Mosquitoes are bad news, but it is time for some perspective. The risk of contracting West Nile Virus is inconsequential compared to the life-threatening risks associated with driving a car, smoking, food-borne illness and obesity. Annually in the U.S., there are many more cases of bubonic plague than West Nile Virus.

The simple fact is that mosquitoes are a part of our natural world, like it or not. Fortunately, in our area, most do not carry infectious diseases. The only species of mosquito in the wild that has been found to carry West Nile Virus, Culex pipiens, is not active during the day. Also, this species has a very limited flight range, measured in hundreds of yards rather than miles.

If this common house mosquito is around your home, chances are that either you or your neighbors are providing the necessary habitat for the insects to breed. Eliminating habitat is the key to controlling mosquitoes. If you do not provide an area for adults to deposit eggs, or do clean out potential breeding area periodically, the life cycle of the insect will be disrupted and no new mosquitoes will emerge.

Mosquitoes need water, primarily still or stagnant water rich in organic matter upon which mosquito larvae can feed. Among the most common locations for this habitat are the saucers gardeners frequently place under potted plants, especially on decks and patios. One option is to remove the saucers altogether, or at least dump them every couple of days.

For balcony and rooftop gardeners, self-watering containers have become increasingly popular. However, the reservoir beneath the container can breed thousands of larvae. As most of these containers cannot be emptied, an alternative is to tape over the access slot or hole used for filling the pot. This will keep out adult mosquitoes and trap existing larvae inside. Any other containers around the garden, such as watering cans, vases, buckets and wheelbarrows, also should be emptied and either stored indoors when not in use or turned upside down.

For gardeners who like to root cuttings in jars and bottles outdoors, emptying the container and refilling it with fresh water every couple of days is advisable. Fresh water will encourage rooting and help eliminate mosquito larvae.

Dripping outdoor faucets should be fixed immediately, both to conserve water and prevent puddles from developing and providing habitat. Also check on rain gutters and downspout areas, especially if you use corrugated plastic pipe to divert water across your lawn. Cover rain barrels with a fine mesh, such as window screening, to keep out mosquitoes. And make sure air conditioning units are not creating puddles as they drain condensed moisture.

Some yards have natural depressions that can form impromptu ponds or bogs during rainy weather. Correct such areas either through grading, which can be expensive, or by creating natural garden areas with moisture-loving plants that can take up excess water and convert it to flowers and foliage.

Ornamental ponds have grown in popularity, thanks to easily available and inexpensive pond liners and supplies. If the pond is stocked with fish, any eggs or larvae will be consumed readily. Aerate, filter or add fish to ponds merely hosting water lilies or other plants, or nothing at all. Even a simple dollar's worth of goldfish will control mosquito populations. Maintain ponds without electrical access with any one of several models of solar-powered pumps and filters.

One unfortunate side-effect of public concern with West Nile Virus is that people are dumping or removing birdbaths. Empty and replace the water in birdbaths every two to four days, both to prevent the spread of avian diseases and to eliminate breeding areas. But removing birdbaths altogether can actually prove a hardship for smaller songbirds, like goldfinches, who easily overheat in summer conditions and require safe havens to cool off, especially as natural water bodies are becoming more scarce.

In addition to typical garden areas, address a number of other mosquito breeding locations. A basic rule of thumb is that if it can hold water, it can breed mosquitoes. Tarps draped over woodpiles or lawnmowers can provide depressions that quickly become mosquito pools. Empty them immediately and rearrange the tarp so that it sheds rainwater. Tarps or covers over pools may keep out leaves and debris, but rainwater settling atop the tarp becomes prime mosquito habitat. A pump may be necessary to drain pool covers.

Wading pools, however small, can invite mosquito activity. Empty them after use and store them on their side, or deflate them. Simply turning the pool upside down will only provide a smaller catch basin for rainwater.

Watch out for water captured in uncovered trash cans or upturned trash can lids. Consider drilling holes to facilitate drainage. Recycling containers left outdoors also can trap water, as can bottles or cans left in the blue bin for more than four days. Again, consider drilling holes in the corners and handles of bins to ensure proper drainage at all times.

Finally, after eliminating or addressing the standing water on your property, think about becoming proactive. After all, getting rid of mosquitoes in your yard does not stop them from breeding in your neighbor's yard. Spread the word to the folks next door and speak up at community association meetings. Working together, your neighborhood should set about identifying potential habitat sites, one backyard at a time. Eventually, you will accomplish what no amount of pesticide ever achieved as you rid your immediate community of mosquitoes naturally and safely.

Copyright 2009, Joseph M. Keyser; illustrations by Tony Fitch.