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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morning glory has attractive flower but is pesty
Photo 3 of 4Morning glory has the potential to grow into a backyard pest.

Morning Glory (3 of 4)

Ipomoea spp
Though certainly not so environmentally or economically damaging as the two previous examples, morning glory is another flowering vine that has attractive blooms but which may ultimately grow into a backyard pest. Morning glory seeds are available at most garden centers, and the plant is often introduced deliberately -- and is even sought after--by gardeners for its beautiful, trumpet-shaped blossoms. The vine's rapid growth and spread, however, can eventually turn it into something of a problem. Once this plant is established, it's quite difficult to eliminate since its hard seeds can stay dormant in the soil for long periods and may germinate even five or 10 years after the parent plant has died.

Other common species "masquerading" as desirable landscape plants, but that are considered invasives, include honeysuckle (Lonicera spp.), English ivy (Hedera helix), privet hedge (Ligustrum spp.), tree-of-heaven (Ailanthus altissima), mimosa (Albizia julibrissin) and Japanese wisteria (Wisteria floribunda).

These are just a few of the most common plant species that have been categorized as invasive. A great deal more information about damaging invasive plants species can be found online simply by searching on the word "invasives." And, according to Robert Norris, perhaps the best place to go for information on problem plants in your area is your local cooperative extension. They're likely to know about the most common pest plants in your region of the country and what you might be able to do to help remove or control them. They'll likely also have recommendations for some desirable native plants that you can grow as an alternative to exotic and potentially invasive species.

Weed Control Tip: As the case of the morning glory seeds amply illustrates, one year of seed production can result in a weed problem that may last for many years. The best way to eradicate weeds is, whenever possible, eliminate them early -- before they've gone to seed.

Green Earth Factoid: As a growing body of scientific evidence indicates, the earth is undergoing a global rise in temperatures that is likely tied to increasing proportions of greenhouse gasses like CO2 building up in the atmosphere. A number of carefully controlled scientific studies have shown that this climatic shift is having significant impact on plant and animal species in many locations all over the globe -- including, in some cases, how and where certain plants grow. And in fact, recent studies indicate that it is frequently the opportunistic and invasive types plants, such as some woody vines, that benefit most readily by this global climate change -- possibly at the expense of mature trees and forests. One study at Duke University showed that increases in carbon dioxide gasses is particularly beneficial to one particularly noxious plant -- poison ivy. The study demonstrated that increased levels of carbon dioxide not only boosted poison ivy growth by as much as 150 percent, but it also caused the plant to produce more of the compound urushiol, the toxin responsible for skin rashes in humans.

Next Photo: Weed Control Basics