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Here are just a few old garden plants now deemed troublesome over wide areas of temperate North America. For more information on weeds in your region, see "Sources and Resources."
Japanese barberry (Berberis thunbergii). This spiny shrub with red berries came to this country in the late 1800s and is a popular foundation plant.
Russian olive (Eleagnus angustifolia). Promoted for wildlife habitat and erosion control, it may tempt the gardener with its silvery willowlike leaves and fragrant late spring flowers.
Burning bush (Euonymous alatus). A shrub introduced in the 1860s and still sold widely for its intense, almost magenta fall color.
English ivy (Hedera helix). Brought to America in Colonial days, it can damage mortar if you pull it from masonry walls. Clip back all you can and spray any regrowth.
Purple loosestrife (Lythrym salicaria). Introduced in the early 1800s and popular for tall purple flower spikes that attract butterflies. Extremely damaging to wetlands and illegal in some Upper Midwest states.
Princess tree (Paulownia tomentosa). Introduced from Asia as an ornamental about 60 years ago for its big purple flowers.
Jetbead (Rhodotypos scandens). Not a widespread problem yet, it was a darling of gardens early in this century for its white spring flowers, shiny black fruits, and ability to grow in any soil, sun or shade, wet or dry, and reproduce easily. (Such selling points are often a red flag.)
Japanese spirea (Spiraea japonica). Still sold for "old-fashioned gardens," this has flat pink flowers rather than the white of some other varieties. |
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An old house usually translates to an old landscape. If you're lucky, you'll inherit some fine old heirloom shrubs that only need a bit of pruning. Depending on where you live, though, you may also fall heir to some of the terrors of the plant world—those becoming infamous as "alien invasives." These go far beyond a few dandelions spotting up an otherwise flawless lawn; they choke out desirable plants, attack masonry and gutters, pull down large tree limbs, and escape into nearby parks or open fields that may have been one of your home's selling points. For the last reason, these plants get a lot of attention from National Park Service biologists and others who serve as restorers of our natural landscapes. In these areas, alien invasives can wipe out native species that birds, butterflies, fish, and other animals depend on for food and shelter, not to mention tramping roughshod over ephemeral wildflowers like lady-slippers and trilliums. They also get attention when they interfere with commerce by destroying farm crops and waterways. For the homeowner they can be simply an annoyance, but a persistent one, since they've made it to the "most wanted" list by dint of prodigious survival skills: production of countless tiny seeds, berries that birds spread, or roots that "sucker" to form thickets or reproduce from the tiniest piece left underground, like the brooms that Mickey Mouse chopped up in Fantasia. Who are the bad guys in your neighborhood? It depends on your climate. Floridians can be overtaken by scheffelera and jasmine—houseplants for the rest of us. In the West, pure botanical evil is represented by the tamarisk, a pink-flowering tree that is a mere curiosity in the Mid-Atlantic. Old-house owners may find themselves beset by vegetation once deliberately planted for utility or beauty, and still sold by nurseries or recommended by well-meaning friends or even state agencies. No one today would be tempted to plant kudzu, the poster child of plants gone amuck. Yet after the Japanese included it in an ornamental garden at the 1876 Centennial Exposition in Philadelphia, gardeners sought it eagerly for its huge leaves and fragrant flowers. Its rapid growth—up to a foot a day—made it perfect for shading big Victorian porches. The Japanese introduced the honey-scented vining honeysuckle as an ornamental in 1806; it cuts into the bark of young trees and can pull them to the ground. Along the ground it can spread a net of tripwires. Bush honeysuckle, with similar flowers and showy fruits, has also earned weed status. You may hear English ivy (brought from Eurasia in Colonial times) recommended to control erosion on banks, or to serve as a lawn substitute. In the Mid-Atlantic and Southeast and on the West Coast it eats up forest floors and, by forming heavy mats on tree limbs, sets them up for storm damage. Other garden plants that have become flora non grata in a wide swatch of the temperate United States include Chinese privet (Ligustrum vulgare, used for hedges), oriental bittersweet (an orange-berried vine once recommended by A.J. Downing), vinca (the blue-flowered groundcover), and Japanese wisteria (see "Beauties That Have Become Beasts" page 38).
Control Methods
Mechanical Means Mow and mulch This is a truly low-tech approach when you can't get around to something more permanent. Mow or weed-whack first if possible, then smother low-growing plants with heavy cardboard, multiple layers of newspaper, or black plastic. Uproot by hand Digit power can be surprisingly effective when the ground is wet. Pull annuals before they've set seed. Uproot with hand tools A short-handled three-pronged claw is useful for relatively tame groundcovers like vinca. For a more vigorous mass of vines like honeysuckle, chop into the tangle with shears, then remove the pieces with a long-handled claw or rake. Hand pull the root when you expose it. For woody plants, some pros swear by the Weed Wrench, a tool that grips the stem of a small tree or shrub between clamps; the user rocks back and forth to pop the plant out of the ground. These come in four sizes and the biggest, which handles 2 1/2½ stems, costs $189. A lighter weight approach for shallow-rooted plants is the Root Talon, a pickaxe-like tool with a gripper that costs about $50. Girdling This cuts off water and nutrients to weed trees. Cut a strip about 2½ wide into the bark and the cambium layer beneath it, all the way around the tree about 6½ from the ground.
Chemical Means Sprayers For large infestations buy a backpack sprayer; set it on a narrow stream to spare nearby garden plants or natives. Wear long pants and sleeves, rubber gloves, and boots. Avoid spraying on windy days and hot days. (Heat makes the chemical volatile so it settles on things other than the target plants—like your eyes.) To get in close on a few isolated weeds that are surrounded by valuable plants, look for a glyphosate foam called Sure-Shot or paint on the herbicide with a brush. Stump and paint To prevent regrowth on a tree too big to pull, saw it off as flush to the ground as possible and paint it with concentrated herbicide (undiluted glyphosate or triclophyr). Hack and squirt For trees too big for the tools you have at hand, chop several "frills" into the bark with a machete, then squirt in glyphosate or triclophyr. It may take a few days for plants to look injured and several weeks to die. Watch for regrowth and keep whacking them back to deprive the roots of food: Thug plants didn't get their evil reputations by being wimpy adversaries.
Sources and Resources
www.mdflora.org
http://tncweeds.ucdavis.edu Invasive Plants: Weeds of the Global Garden Published by the Brooklyn Botanic Garden, $8.95. Describes invasive plants by date of introduction and regions where they are a problem. Order at www.bbg.org/gar2/topics/sustainable/handbooks/ invasiveplants/index.html or call (718) 623-7286. New Tribe, (866) 223-3371. Weed Wrench. Lampe Design, (866) 334-9964. Root Talon.
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