The Dirty Dozen: 12 Plants to Avoid

Messy, invasive or both, some of these bad boys will choke out other plants or destroy buildings. Here's help spotting these nightmare plants.

1. Purple loosestrife
Purple loosestrife (Lythrum salicaria, not related to gooseneck loosestrife) is the bad girl of gardens across the United States. Its nicknames -- "marsh monster" and "beautiful killer" -- give clues to its aggressive tendencies. The plant chokes out native plants and just about anything else in its path. Lythrum salicaria is the wild variety. Its cultivated cousins -- Morden Pink, Morden Gleam and Dropmore Purple -- are just as bad, though you'll find them in a nursery or a plant sale. It's lovely looking: The rangy purple loosestrife reaches 4 to 7 feet tall with heads of blazing magenta flowers. But don't fall for its good looks. "Each plant produces about 2.5 million seeds annually and can live up to 20 years," says Sarada Krishnan, director of horticulture at the Denver Botanic Gardens. The seed is spread by insects, wind, water and animals. Weed sprays don't kill it, and even the tiniest piece of broken root can start a new plant.

2. The female maidenhair tree (Ginkgo)
The maidenhair tree (Ginkgo biloba) can be grown in most parts of the United States. The problem is that the female ginkgo is obnoxiously messy. It drops a mass of slippery, evil-smelling fruit -- some liken the stench to vomit, others say it smells like rancid butter. If ever there was a reason for gender discrimination, this is it. It's not easy to distinguish the girls from the boys, so get help in identifying the males from a nursery expert before you buy. In the right environment, the ginkgo is an asset as a tall (up to 150 feet or more), deep-rooted, fast-growing, attractive shade tree.

3. Yellow toadflax
Yellow toadflax (Linaria vulgaris) also goes by the evocative name "butter and eggs." What could be cuter than these stalks of miniature yellow snapdragons, you think. Hah! Yellow toadflax has earned a bad reputation in the northern and western United States for invading gardens, pastures and range land, crowding out native plants, ruining wildlife habitat and upsetting the balance of natural ecosystems. The chances are that you won't have to find it: It'll find you. Seeds blow in on the wind and take root in your garden, producing pretty, knee-high stalks of flowers. Once settled, its extensive system of roots resists control, even by herbicides. Your best bet: Pull it out when you first see it and take heroic measures -- cutting and pulling -- to keep it from going to seed.   

4. Silver maple tree
Silver maple (Acer saccharinum) is a handsome tree with an unfortunate tendency to hog the show. It grows so fast -- between three and seven feet a year -- that the United States Department of Agriculture advises farmers to consider it as a biofuel crop. The leaves of this North American native are large, with deep cuts in the edges. The silver maple sends down a messy rain of little red catkins in spring, but its worst fault is the weakness of its wood. The limbs are brittle, so they break and splinter in windstorms and freezing conditions. Jeff Cox, author of "Perennial All-Stars: The 150 Best Perennials for Great-Looking, Trouble-Free Gardens" once had a silver maple and calls it "a passel of trouble at all times."

5. English ivy
English ivy (Hedera helix) is the romantic green vine that clings to old English cottages and makes them look old and English. But you pay a price for all that cuteness. It's found just about everywhere in the United States and Canada, to the regret of many gardeners. A single planting can quickly cover a garden or a shed. Or even a house. It sends out aerial rootlets that attach to the most challenging vertical surface. It's destructive in a bunch of ways: Its tendency to hold moisture encourages rot; it destroys paint; and the roots creep into the mortar between bricks, wrecking masonry. Those who've attempted (usually unsuccessfully) to eradicate it have tried everything from boiling water, vinegar and herbicides to burning it with a propane torch or smothering it with newspapers and blankets of plastic. The best advice: Don't plant it.    

6. Bishop's weed
Bishop's weed (Aegopodium podagraria) -- aka goutweed or ground elder -- is so respectable-looking that beginning gardeners often are seduced by the ease with which this low-growing beauty fills up an empty spot in the garden. It grows in most parts of the country, thriving in poor soil and dry conditions. It produces a frothy white flower in late spring and summer, and the green-and-white variegated type of bishop's weed (Aegopodium podagraria 'Variegatum') has extra pizzazz. By the time you've realized it's a problem, you're stuck with an impossible-to-destroy network of delicate but persistent roots. Bishop's weed dies back in winter, but don’t worry: It'll return in spring. Still, many gardeners like it. Some manage to contain it by using it where the edge of a garden meets the lawn so they can keep it in check on one side by mowing. Otherwise, you must pull up as much of the plant as you can several times a year just to keep it contained in one spot. Expert Jeff Cox's advice: "Avoid it like the plague."

7. Japanese honeysuckle
Japanese honeysuckle (Lonicera japonica), also called Hall’s honeysuckle, has a lot to recommend it: It's happy just about everywhere and doesn't need much water; when white flowers blanket the vine in late spring and early summer, the fragrance is intoxicating. Just one plant, however, can grow to 50 or 60 feet long. This is a plant that's not happy until it's choked and smothered everything around it. And once installed in your garden, it's likely to be your companion forever. "I hire guys to come and rip it out," gardening expert and author Jeff Cox says, "but it grows back in a few years."   

8. Bouncingbet
Bouncingbet (Saponaria officinalis) -- aka soapwort -- grows in the northern half of the United States. A small soapwort plant quickly becomes a lovely, low-growing mat of green and, for about a month in late spring, it is studded with tiny, fragrant pink flowers, like a sky full of pink stars. Many gardeners adore its cottage-garden effect. It's unruly only if you let the flowers produce seed heads. Once bouncingbet has gone to seed, you're stuck with a zillion baby plants popping up everywhere -- and reproducing. This plant isn't an awful pest, but you'll need patience to keep it under control. Here's how: Shortly after the blossoms have faded, use scissors or garden shears to remove all the tiny dead flowers. Throw them away so that no seeds are left in your garden.

9. Gooseneck loosestrife
Gooseneck yellow loosestrife (Lysimachia clethroides) -- also called Japanese loosestrife or shepherd's crook -- grows happily most everywhere in the United States. It's a lovely plant with graceful, nodding spires of white flowers that bloom from spring through fall on tall green stalks. Too bad it spreads like crazy. Don't be tempted to use this plant, an Asian native which, when removed from the predators in its natural habitat, becomes a pest. "That stuff will take over your garden," warns Jeff Cox, author of "Perennial All-Stars: The 150 Best Perennials for Great-Looking, Trouble-Free Gardens." Gooseneck loosestrife is double trouble, in fact, because it spreads both by producing zillions of teeny black seeds and also through its underground network of rhizomes.    

10. Trumpet creeper: Destroyer of buildings
The trumpet vine or trumpet creeper (Campsis radicans) can be hell on roots if you plant it in the wrong place. Drape it over an arbor, a wall, a fence -- "or over an old wrecked car if you don't want to look at the car," says garden expert Jeff Cox. But don't let it near a building. "It'll tear the building to shreds," Cox says. "It'll pry the boards off." If you simply must have this plant, grow it on a trellis and prune it regularly. The trick to avoiding trouble with such bad plants is to understand their habits and, if you are determined to have them, fit them into spots where their idiosyncrasies don't cause trouble.   

11. Leafy spurge
Leafy spurge (Euphorbia esula) is simply a menace. It's common in the Great Plains and Rocky Mountain states. You probably won't find it in nurseries. Beginning gardeners are likely to pick it up at a garden club plant sale or as a gift from another novice gardener. Even if you're happy to have the foot-high yellow plumes lighting up your garden in early spring, your neighbors will want to toss you out of town if the wind blows seeds into their gardens. That's because leafy spurge is the black sheep of the 2,000-member euphorbia family, which includes many fabulous garden plants. Like something out of a horror movie, it spreads both by deep, threadlike roots reaching several feet underground and by seed. Here's the worst part: Once it's established, pulling it out just stimulates the root system to produce even more plants, and even herbicide sprays are ineffective. They may kill the flowers but the roots live on, so it'll be back.

12. Ox-eye daisy
Ox-eye daisy (Leucanthemum vulgare). No one could blame you for welcoming the sight of so many sunny daisies in your garden, popping up unexpectedly from seed blown in on the wind. Or, you might have bought this plant at a nursery, or perhaps it came in a wildflower seed mix. The ox-eye daisy grows in pretty little clumps, white petals arrayed around cheerful yellow centers, nodding in the midsummer breeze atop stalks one to three feet tall. They're found everywhere in the United States. The ox-eye daisy is a cousin of common chamomile, a plant used to make a popular, soothing tea. The ox-eye leaves can actually be plucked and eaten in salads, though not many people do it. But let this happy little plant take over your garden and you're in for a lot of work, since each plant produces more than 500 seeds that take root just about anywhere. Some gardeners enjoy keeping a few of the plants but they keep a careful watch on the flowers and quickly "dead-head" them -- the term for cutting flowers off the stem -- before they go to seed. If that should happen, pull out the plants as they emerge next year, leaving just a few to enjoy. 

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