DIY Network

What Every Gardener Should Know About Weeds and Invasives

Kristine Hanson of The Dirt on Gardening talks with Robert Norris, professor emeritus of plant sciences at University of California Davis, about weeds and invasive plants.

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some plants are invasive and cause problems
Photo 1 of 4Common nursery plants that can cause problems: morning glory, water hyacinth and Vinca.

Weeds and Invasives(1 of 4)

Every spring, there's a nagging word that creeps into the back of every gardener's mind, and that word is weeds -- a single and unpleasant syllable that brings with it thoughts of stooping among the tomato vines or behind the azalea bushes, until your back hurts, plucking hard-to-reach space invaders while enduring summer heat and buzzing insects.

Making matters worse, it's possible that you've brought "weeds" home from your local nursery without even knowing it. Some plants sold as groundcover or ornamentals can, in fact, become unwelcome residents of your garden as they spread beyond your control. Vinca, for instsance, is a common groundcover that commonly outgrows its welcome in the backyard setting.

Worst of all, certain kinds of weeds can go well beyond a simple nuisance to gardeners. Personifying, as some do, that key phrase "vigorous growth," some plant species, if allowed to grow unchecked, can cause serious and even devastating environmental problems.

A Weed By Any Other Name

Even the term "weed" is a bit problematic and ambiguous since one person's weed might, for example, be another person's ornamental grass or flowering vine. Merriam-Webster defines weed (n) as: "a plant that is not valued where it is growing and is usually of vigorous growth; especially one that tends to overgrow or choke out more desirable plants." So if we think of "weed" in a general sense as any undesirable or nuisance plant, it's a disturbing thought that some of those can be introduced -- either by accident or with good intention -- by the gardener.

An even more disturbing thought is the fact that some exotic plants species can cause problems far beyond the boundaries of your backyard, actually causing serious and widespread damage to natural habitats and ecosystems. Plant specialist Robert Norris explains how many plants, innocently purchased from nurseries or plant suppliers, can become invasive and profoundly problematic when introduced in certain settings or under the "wrong" set of circumstances.

"When a plant gets into an ecosystem," says Norris, "it's sometimes possible that it will literally take over that ecosystem, displacing everything that was there -- or nearly everything that was there -- before."

Next Photo: Water Hyacinth