Sunday, September 26, 2010

Don't Get Bamboozled!

A common axiom in gardening is putting the right plant in the right place. Where bamboo is concerned, most people think that the only appropriate location is somewhere on the far side of hell. Bamboo is cherished and ardently defended as a vigorous landscape screen by some, although it is usually cursed as an invasive, unstoppable menace by most others, especially irate neighbors who find spikes and spears shooting up in their lawn and garden beds.

There are more than 750 species of bamboo plants which have been introduced to North America from Asia, the Caribbean, and Latin America. Most of these woody grasses (yes, they are actually grasses!) fall within the genera Bambusa, Pseudosasa, and Phyllostachys, and are renowned for growing upwards of 16 to 40 feet, with a cane or “culm” diameter ranging from one to six inches. Many also experience a general die-back after about a dozen years, usually after flowering, which will leave a dead, yellowed bamboo jungle, until new growth repopulates the grove.

Some species are considered “clumping,” which are generally well-behaved, while the more insidious specimens are called “running bamboos,” which will swiftly produce an impenetrable and monocultural thicket as they exert their own manifest destiny. Among the most commonly sold, planted, and (ultimately) loathed of runners is Golden Bamboo (Phyllostachys aurea).

These exotic invasive bamboos have caused feuds just shy of the infamous Hatfield and McCoy dust-up. Lawsuits have been filed, bulldozers mobilized, and concrete barriers poured. And yet, for all that, people looking to screen their yards from neighbors continue to plant running bamboos, especially in narrow spaces between properties or along fence lines.

Happily, there are attractive and non-invasive alternatives to bamboo blight, but first we should address how best to control and eradicate these invaders.

To keep bamboos from running, a rhizome barrier should be used. Bamboos very seldom produce seeds, and use rhizomes, or horizontal underground roots, to spread outward. To stop this march, a barrier two-three feet deep is essential, with about two inches rising above the soil surface. Slant the barrier outward near the top to ensure that rhizomes hitting your blockade will grow upward, and not down and eventually under the barrier. Keep an eye out and cut off any roots that attempt to grow over the top. Barriers can be made from metal or concrete, although heavy 60 mil plastic is the most readily available and affordable.

Clumps of bamboo can also be dug out, as the roots are actually quite shallow. Be sure to remove any and all pieces of the rootstock, including wayward rhizomes, and keep an eye out for future incursions.

A somewhat easier approach is to cut bamboo shoots as close to the ground as possible, and thereafter snip or mow down any new shoots or pesky regrowth. Eventually, you will starve the rootstock and the plant will die, although you will need to patrol the area on a regular basis for a year or so. This technique is best used on bamboo entering your yard from a neighboring property. In fact, some homeowners simply mow down any shoots in their lawns when they cut their grass, and have seen thumb-thick shoots eventually replaced by pencil-thin sprouts, just before they disappear altogether.

For quicker, more thorough results, Jan Ferrigan, an invasive plant program manager in Virginia, recommends cutting down bamboo shoots and applying Roundup or a similar glyphosate herbicide directly inside the now-open stem, and painting the outer surface of the culm. Jan suggests carefully using the herbicide at a 25 percent concentrated solution, not the typically diluted two percent used for routine spraying. And fall is the usually recommended time for application.

Naturally, the best solution is not to plant exotic bamboos at all. And the finest alternative is, not surprisingly, a native bamboo. Generally called canebrake bamboo (Arundinaria gigantea), or southern cane, this species used to cover enormous stretches of riparian “bottom land” from the mid-Atlantic to the Midwest prairies, down through the southeast, and along the Gulf states. Amazingly, before European colonization, native Americans lived among canebrake groves several miles in width, running up to 100 miles in length. Today, there are only scattered patches of these lush thickets.

Homeowners looking for a tall, dense, yet elegant, living fence need look no further. Canebrake can reach 12 to 18 feet or more, with half- to three-quarter inch canes and medium to dark green foliage year-round. However, when shopping around, don’t confuse this species with switch cane (A. tecta), which is smaller, low growing, and more suited as a groundcover plant. And while very few garden centers and nurseries seem to carry canebrake, there are numerous sources online and through mail-order catalogs, with prices ranging from 15 to 25 dollars for one and two gallon containers.

Not interested in bamboo at all? Consider arborvitae (Thuja occidentalis) as an alternate evergreen screen. The cultivar Emerald Green is probably the most popular of standard arborvitae, growing 15-20 feet, with a spread of four-six feet. Its lustrous gem-green foliage is tolerant of cold winters and hot summers, although, as a native of the northeast, it would prefer to be watered during dry periods, and mulched three to four inches deep to retain soil moisture.

Emerald Green can be pruned if or as desired in early spring, and is often considered superior to the much overused Leyland cypress, which could also work as a screen, although it can reach 60 feet and would require substantial pruning to achieve the same effect. Other desirable cultivars include both ‘Nigra,’ which remains dark green even through the winter, featuring a pyramidal form reaching 15-25 feet and five-eight feet wide, and ‘Pyramidalis,’ with softer, bright green needles, growing to 15 feet with a four foot spread.

Another clear winner is Irish juniper (Juniperus communis ‘Hibernica’) with bluish-green foliage, and a columnar form reaching 10-12 feet. This juniper is drought tolerant, with dense upright branches. Some nurseries indicate that it can reach 15 feet with only a narrow two-four foot spread.

There are also numerous species of yews suitable for narrow space screening. All are able to handle heavy pruning and shaping, and contrast their dark green foliage with bright, fleshy red or yellowish-red berries, called arils.

Perhaps most prized of all is Irish yew (Taxus baccata ‘Fastigiata’), which is actually an English or common yew, easily growing from 15-30 feet tall, with a four-eight foot spread. [It is the most commonly grown species in Europe, and has been in use for well over 200 years.] The needles are a striking blackish-green, although other cultivars, such as ‘Fastigiata Aurea,’ while similar in form, actually feature golden foliage on its new spring growth.

Japanese Yews (Taxus cuspidata) generally tend to have a broader spread and lower growth habit, and often quite a slow growth rate. However, cross Japanese and English yews and you’ll find a hybrid (Taxus x media) showcasing some of the best assets of each parent. Many of the outstanding cultivars for living screens were developed or discovered on my native Long Island, including several by famed nurseryman Henry Hicks. The specimen bearing his name, Hicks yew (Taxus x media ‘Hicksii’), is columnar in form, 12-20 feet high, and six-ten feet across, with glossy needles, deep green on top and a pale green underneath.

Lastly, Eastern hemlock (Tsuga canadenensis) has long be valued for its light, airy needles and graceful branches, which readily accommodate heavy pruning to create a lush, dense hedge. Left on its own, however, the tree will reach 60 feet with wider spaced branches.

Copyright 2010, Joseph M. Keyser

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