The winter of 2010 has had a stranglehold on the Sandhills for several months, giving local gardeners little incentive to think about things in the garden. No matter how far away it seems, spring will eventually come. Gardeners should take advantage of this downtime to think about what plants they would like in their landscape; conversely, they need to learn what plants they should avoid. Some plants, although beautiful when first introduced to the landscape, can spread rapidly, take over the yard and escape into the wild.

Free Workshop

Gardeners should keep in mind that it is best to be informed about the growing habits of plants before going on a shopping spree at the nursery or placing an order from a nursery catalog. It also helps to step back and evaluate the plants that are currently growing in the garden to determine which ones might eventually take over.

Local biologist Tracy Rush will provide that information at a workshop presented by the Greenway Wildlife Habitat Committee, which is part of the Pinehurst Conservation Commission. The workshop, “Got Invasives? What’s in Your Backyard?” will cover landscaping plants that are invasive in the Sandhills, how to control them before they take over and how to identify native plants that can serve as useful alternatives. The workshop, which is free to the public, will be presented from 10:30 a.m. to noon Saturday, Feb. 27, at the Village Hall, 395 Magnolia Road in Pinehurst.

Rush is program coordinator for the North Carolina Sandhills Weed Management Area (NCSWMA), a partnership of government agencies, conservation groups, individuals and others interested in managing invasive plants in the Sandhills. During her 17 years working as a biologist in the Sandhills, Rush says she has observed firsthand the impacts that invasive plants can have on the ecosystem.

“As program coordinator for the NCSWMA, it is my job to manage the invasive plant control/eradication effort and invasive plant education outreach program,” she says.

Exotics vs. Natives

In order to understand what makes a plant invasive, it is important to understand the distinction between native and exotic species.

Rush defines “native” species as those that naturally occur in an area.

“They have not been introduced by human action,” she says. “They have evolved over time with the biological and physical factors specific to an area including climate, soil and rainfall.

“An ‘exotic’ species is the opposite of a native species. Exotic is synonymous with nonnative, alien, nonindigenous and introduced.”

A plant can be native to other parts of North Carolina but not be native to the Sandhills. Eastern hemlock, native to the mountains of North Carolina, is considered an exotic in the Sandhills.

Rush describes an invasive plant as “an exotic plant that is capable of moving aggressively into a habitat and monopolizing resources such as light, nutrients, water and space to the detriment of native species. All invasives are exotic but not all exotics are invasive.”

Rush says that invasive plants share a number of characteristics.

“Invasive plants tend to mature quickly, produce large quantities of seeds and/or fruit, have seeds that are easily dispersed by wind, water or birds and reproduce vegetatively (from pieces of root or stem),” she says. “They also tend to be generalists that can grow in many different conditions; grow rapidly; generate dense shade; have aggressive root systems; inhibit the growth of other plants around them; thrive on disturbed soil and are generally pest-free without natural predators, competitors or pests to keep them in check.”

Plants to Avoid

When asked about the most troublesome invasive plants in the Sandhills, Rush has a long list of plants, all of which have been purposely introduced into local landscapes but have now invaded natural areas and become a problem in local gardens. Plants introduced for use in gardens include Chinese privet; Chinaberry (as a shade tree for its colorful flowers and berries); mimosa (as an ornamental tree for its showy flowers and fern-like leaves); and Chinese and Japanese wisteria (as ornamental vines for their large, showy flowers).

Other invasive plants have been introduced for erosion control and wildlife habitat. These include Japanese honeysuckle and weeping lovegrass. Chinese lespedeza, introduced for soil conservation, and wildlife and livestock forage, is still being planted for food and cover for quail and for erosion control at construction sites. Other invasive plants on Rush’s list that are just beginning to appear in natural areas include the Bradford pear, thorny olive, Chinese silver grass and nandina.

How Did They Get Here?

Most invasives have been introduced intentionally for horticultural or other uses. According to Rush, the New England Wildflower Society Web site reports that 60 percent have been introduced by arboretums, botanic gardens and home gardeners for horticultural uses; 30 percent have been introduced for conservation activities, mostly for screening, windbreak, erosion control, and to supply food and cover for wildlife. Only 10 percent have been introduced accidentally. Purple loosestrife was brought to the U.S. in ballast water in the hold of a ship and then later used for horticultural purposes.

When asked how invasive plants get into the area, Rush responds that invasive plants are readily available in North Carolina, either from nurseries or by bringing them in from other areas of the state or from other states. Very few landscaping plants are regulated in North Carolina and it is difficult to get plants added to the list of regulated plants.

“Most invasives are hardy, easy to grow and easy to propagate, traits making them ideal for the nursery industry,” she says. “In addition, we consumers continue to purchase these plants because we are also unaware of their invasive potential. It’s simple supply and demand!”

One goal of the NCSWMA is to educate the nursery and landscaping industry because they are often unaware of the invasive potential of many of the plants they sell.

How They Spread

Local gardeners may wonder how plants commonly used in local landscapes escape into wild areas. Rush tells the story of the Bradford pear, which serves as a good example.

“The original Bradford pear, introduced in the early 1900s, was not invasive,” she says. “It produced sterile fruit. Then, because the original Bradford pear was prone to weakness (breaking apart in wind and ice storms), new cultivars were introduced. These cultivars started cross-pollinating with the original cultivar, producing viable fruit and seed.”

Rush says that it is just starting to appear in the wild here in the Sandhills, and the goal is to prevent it from becoming a widespread problem here as it has in other areas. Using a program called early detection/rapid response may control invasive species while they are still manageable and do not cost hundreds of thousands of dollars to control.

Nandina is another plant widely used in the Sandhills that is increasingly escaping and spreading into woodlands. It is not now as destructive here as in states south of North Carolina, but Rush fears that its widespread use creates the potential for it to become a real problem. Although some cultivars do not produce viable seeds and others produce no fruits, this could change as it did for the Bradford pear.

The Solution

So what should local gardeners do to remove invasive plants from the garden?

Rush is quick to say, “I don’t suggest that you rip out all of your current landscaping! Many of us have inherited our landscaping from the previous homeowner, including invasive plants. Many of these are well established and hard to easily replace.

“First figure out which plants in your yard are invasive and slowly replace these invasives with native or noninvasive plants. It will take some work to remove some invasives that are well established. The best way to remove vines is to cut the vine close to the ground and spray the stem with an herbicide such as Roundup. Then you will need to spray any new sprouts that come up. It may take several years to completely control some species.”

As for finding replacements for those invasive plants? Rush says there are plenty of native and noninvasive plants that are very attractive in the landscape. She adviseds that if you love wisteria, plant the native kind, American wisteria (Wisteria frutescens), which is currently available in the nursery trade.

As for replacement shrubs, Rush says that, although the nursery industry has developed some “sterile” or nonspreading varieties of common invasive landscaping plants such as nandina, it is best to avoid those. There is always the possibility that these “sterile” varieties may over time revert back to their invasive ways as did the Bradford pear. The best solution is to learn about native plants that are attractive and do well in their native environment. She will provide recommendations at the workshop and also recommends a visit to several useful Web sites: www.ncswma.org and www.invasive.org.

Rush offers a last bit of advice.

“In general, we need to stop planting known invasive plants,” she says. “Also, we need to follow this simple rule: Iif you don’t know it, don’t grow it!’ Always check to see if a plant is invasive before plant-ing it.”

For information, call (910) 295-1900 or visit www.villageofpinehurst.org.