In Good Thyme

"Years ago, I was acquainted with a young couple who owned a home on a picturesque river. Concerned for the river bank's slow erosion, they planted bamboo to hold it. They could not have made a poorer choice. Within three years, the bamboo had created a thicket along the shore. The native plants were choked out, including the grasses that provided food and shelter for birds and small mammals. The bamboo's ruthless roots climbed the bank into the garden and overtook the lawn. It marched along the bank onto neighboring property. It was an ecological and aesthetic nightmare.This couple considered themselves environmentally aware, but their uninformed choice of planting was a runaway disaster. Yes, bamboo can be beautiful, but not when planted without forethought. Its roots are undisciplined Olympic-class runners. Unless the gardener puts heavy rubber or metal root barriers in the soil, he will have a bamboo forest. I realize I'll get mail from defensive bamboo aficionados arguing that there are different types of bamboo, and not all of them are invasive. I know that, but I want to make a point about aggressive plants. Beware! Beware the friendly neighbor who has just divided her perennials and offers you a few! Watch out for plant sales that seem to have a zillion of one kind of plant. Why are there so many of them, and why are they selling them so cheaply?Invasive ornamentals are as aggravating as weeds. I recall how delighted I was when I first planted (ITAL) Lychnis coronaria. Its common name sounded medieval and romantic as a princess in a tower - rose campion. Ah, yes, the lovely Lady Campion, with her soft silver foliage and deep magenta flowers. No one told me how prolific was this pale-limbed princess who flung her seed far and wide. The spring following her arrival, my garden was overrun with little fuzzy-leafed (ITAL) Lychnis. Fortunately, they're not difficult to pull, but if you don't, you may have hundreds next year.Another seductress I have banned from my garden is (ITAL) Cerastium tomentosum,known as snow in summer. It's lovely in rockeries and borders when contained, but if you don't watch it, it will blanket the entire bed. The same can be said of bronze fennel. Let it go to seed and you will have it forever.And what's this about shy violets? I rue the day I brought one small violet into the garden. That little plant's far-reaching runners have infringed upon large sections of the shade garden. Be wary, as well, of (ITAL) Campanula rapunculoides.It's Genghis Khan reincarnated as a diminutive lavender bellflower. When aggressors such as these are growing among established plants and shrubs, it's hard to spray them with a non-selective weed killer without damaging desirable specimens. And if you've ever tried to pull them, you know that even a teeny piece of root remaining in the ground will miraculously regenerate. Aaargh!A few weeks ago I took out a vegetable and herb bed and in its place, laid stepping stones. I planted wooly thyme between the stones to soften the path. A few days later, I noticed that tenants of the former herb bed were shooting up through the thyme. I know it's going to be a constant battle to keep those chives from reclaiming that spot. Ornamental grasses are wonderful, but some, such as ribbon grass (ITAL) (Phalaris arundinacea) and blue lyme grass (ITAL)(Leymus arenarius 'Glaucus') have rampaging roots that will take over the world if you allow them to escape. Fountain grass (Pennisetum setaceum) is on the red alert list of non-native pest plants of greatest concern in Oregon and Washington.One of the worst garden invaders is English ivy. It will overtake and destroy native and cultivated plants and is a notorious harbor for rodents. If allowed to climb buildings unfettered, its tentacle-like holdfasts eventually destroy wood and shingles. Some like the look of English ivy in trees. Little do they know that those big, shiny leaves are slowly smothering them.Before you purchase a plant with which you're unfamiliar, do your research. Look it up in that old standby, the Sunset Western Garden Book; there's usually one available for customers to peruse at garden shops. Ask your nursery person, point blank, if the plant is invasive.You probably have your own list of horticultural gatecrashers. I invite you to share it through this column in the hope of sparing other gardeners from Attila the Honeysuckle or Glad the Impaler. OK, OK! Write to me and I'll stop!-------------------Mariana Graham, a writer and former editor, is a Master Gardener certified through the WSU-Island County Cooperative Extension Service.If you have questions or comments, contact her at the Whidbey News Times, 675-6611; fax 675-2732; or e-mail garden tipPlant garlic now for spring harvest. "

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