When the Asian wisteria, Japanese honeysuckle and mimosa tree burst into bloom this spring in their annual spectacle of seduction, you can pull out your camera and capture their loveliness forever.
Or you can reach for your machete, chainsaw and herbicide.
Some of the most popular landscape plants that are tenderly cultivated in Triangle gardens hardly need your assistance: They are deemed by the nation’s botanical authorities as non-native invasives.
Lake Crabtree County Park’s environmental educator Daniel Wheeler described 13 of the most common and most noxious of these invasives Sunday in a public program entitled “Aliens In Your Garden.” The lecture marked the beginning of National Invasive Species Awareness Week.
Wheeler estimated there are more than 100 such plants escaped and naturalized in North Carolina, and he didn’t even bother with horror stories about the ubiquitous kudzu, since the vine is universally known and detested. He warned of one recently escaped plant, Japanese blood grass, as “worse than kudzu” and said the chemical-resistant and fireproof grass is pushing its way north from Georgia and South Carolina.
“Studying invasive species can be a little depressing when you realize how many there are,” Wheeler said during a two-hour presentation. “And part of the problem is that people are still buying and planting them.”
On Tuesday at 5 p.m., Lake Crabtree County Park will offer another program, this one on invasive animals.
Alternative ground cover
The people in attendance Sunday knew that Bradford pears and some bamboos can get out of control, but it came as a surprise that snacking on the leaves of the ever-popular privet bush is poisonous to horses and other domestic animals. Wheeler labeled the Privet as his “Top Ten Public Enemy.”
Women from the Lakeridge Townhomes Grounds Committee in Cary came to learn the best botanical practices for their neighborhood landscape.
“We’re just trying to figure out what’s there, what’s okay, what’s not,” said Nancy Butters, a committee member. “We’re trying to make it a more responsible area.”
Wheeler offered suggestions on native ground covers, climbing vines and flowering trees that can be grown in place of popular invasives. Some, like tulip poplars, are well known; others, like the intoxicatingly fragrant “Maypop” passion fruit vine, are still novelties to many gardeners.
Some invasives, like English ivy, can smother a tree and kill it over time, Wheeler said. Others are almost impossible to extirpate. Lake Crabtree County Park last year undertook a project to eradicate a resilient ground cover called Japanese stiltgrass, using herbicide and teams of high school volunteers. The project is expected to take at least five years because the seeds of this species remain viable at least that long in the ground.
Non-native plants are those that appeared in North America after the arrival of European settlers. Most come from Asia, because North Carolina’s climate is similar to Japan and China. Not all non-natives are labeled as invasives – consider the dandelion, butterfly bush, apple, cherry, peach and many others – which raises a peculiar aspect of botanical classification.
An invasive, Wheeler said, is almost always a plant imported to this country by Europeans as some wondrous amaranth that later turned into a pest to European descendants (as well as to others living here). Thus European tastes are often the measure of good and bad in horticulture, and invasives are plants that are either poisonous, harmful to agriculture or disruptive ecologically.
“The harm they do is usually in terms of humans,” Wheeler said.