Stand up to garden thugs

This horror story starts so innocently. You bring home from the nursery a pretty little flower or a pert green vine. You give this new plant a home in your garden. Water it, feed it and watch it grow.

And grow and grow. It's wondrous how it thrives.

But then, this single plant overwhelms its neighbors, expanding like magic to wipe out the competition. It strangles bushes, topples fences and can invade the house as it grows out of control.

"The British have a term for them: garden thugs," said Don Shor of Davis' Redwood Barn Nursery. "That's exactly what they are."

Many ornamental plants fall into this category. The most notorious: bamboo and mint.

When they sprout into wilderness areas, they become truly invasive, a danger to native species and a public nuisance. According to PlantRight, protecting California from invasive species costs more than$80 million a year.

Shor has a lifetime of experience with these green thugs, especially bamboo. His father was president of the American Bamboo Society.

"That's the No. 1 question we get: How do you control bamboo?" Shor said. "The answer is plant the right kind of bamboo to begin with."

Bamboo comes in running and clumping species. The first send out underground runners that sprout anywhere. The "clumpers" stay contained.

"Everybody's brother-in-law has a horror story about running bamboo," Shor added. "If you plant clumpers, you can get the look without the headaches."

Shor suggested Alfonse Karr clumping bamboo as an example of a well-behaved variety. "It gives you that look that people want, but stays in one place."

Ellen Zagory, horticulture director for the UC Davis Arboretum, has neighbors with running bamboo, which means she has bamboo shoots constantly coming up in her own yard.

"It's really scary," she said. "I've seen concrete patios where every little crack and seam had bamboo coming up. When I see some come up, I dig a big, long trench down as far as I can go and get as much as I can."

Running bamboo may be contained by root barriers, solid sheets of fiberglass or other material buried 2 to 3 feet down.

"But you've got to monitor the barriers," Shor added. "The runners can go right over or under them."

As for mint, Shor planted one spearmint from a 3-inch pot. "It now covers an area 10 feet wide — all from that one tiny plant."

"Mint is No. 1 (among problem plants)," said Joan Coulat of Capital Nursery. "I had a dilly of a time with mint. I'm smarter now. People shouldn't put it in to begin with."

"Powis Castle artemisia (or wormwood) is another that really gets going with low water," Shor said. "Three plants (from 1-gallon cans) now cover a 40-foot stretch along my driveway. It's a cute little plant in the herb garden, but it can really cover the ground."

Cardoon — "like artichokes on steroids" — can be a vegetable gone wild.

"Four seedlings turned into more than 200 plants," Shor said. "They're pretty, but very invasive by seed. My removal technique consisted of three teenage boys, each with two machetes. The seedlings persisted for two to three years and were dispatched immediately with a shovel."

Bee balm is another herbal thug.

"If you really like to divide plants and share them with others, you can grow bee balm," said Judy McClure, coordinator for the Sacramento County UC Cooperative Extension master gardeners. "But if not, it's incredibly invasive."

Local master gardener hot lines get lots of calls about controlling invasive plants, especially in spring when new seedlings grow like crazy.