Everyone has surely noticed by now. It began quietly decades ago and progressed slowly for many years. By way of nearly exponential growth, the invasion of these white trees first became evident here about four or five years ago. This spring the display has been awesome. If you’ve driven around the county, you may have gotten the impression that they are everywhere. We’re talking about ornamental pear trees, of course.
The Bradford pear was introduced a century ago as a sterile cultivar of the Callery pear, a native of China. It quickly found acceptance for ornamental planting due to its fast growth, attractive shape, early spring flowering and colorful fall foliage. Some nurserymen shied away from Bradford pears because its weak wood made them especially susceptible to wind and ice damage. And some people think their flowers stink.
The serious problem with Bradford pears began when they cross-pollinated with other pear species to produce fertile seeds. Birds eat the small pears (a half inch diameter or less) and spread the seeds. The sprouts can grow in a wide range of soils, wet to dry, and are relatively shade tolerant.
Many neighborhoods in Winchester and surroundings have used Bradford pears as specimen plants or to line driveways. Mowing keeps the pear sprouts at bay in this setting. However, when seeds reach open fields that are not mowed regularly, they can take hold quickly, forming dense thickets that tend to crowd out other species.
The Bradford pear is a classic example of an invasive species, a relatively new one in our region. Unfortunately, the tree is still widely available at nurseries and garden centers. Their continued planting poses a serious threat to native ecosystems.
Two other escaped species have already had a dramatic effect on urban and rural landscapes in our area: bush honeysuckle and wintercreeper vine.
Bush honeysuckle, originally touted as a fast-growing hedge, has spread extensively throughout the Bluegrass region. At first it was planted to form a border between neighborhood properties. Then it escaped. Birds ate the berries and spread the seeds. Now honeysuckle has become a pervasive resident along our roadways and fence lines, often growing up to 30 feet high.
Honeysuckle is the first shrub to green up in the spring and one of the last to lose its leaves in the fall. The plants can grow up under the forest canopy and spread profusely, often forming impenetrable colonies that choke out other species. In areas outside the Bluegrass, where this Asian invader has not yet become established, one can still see open woodlands; they present a sharp contrast with our forest understory crowded with honeysuckle thickets.
Wintercreeper (Euonymus fortunei) is perhaps even worse. This evergreen vine, commonly planted as an ornamental groundcover, is extremely difficult to control. Wintercreeper eventually escapes from its planting area and spreads rapidly. It forms a dense groundcover and is very hard to eradicate. Euonymus is cold and shade tolerant; it is one of the few plants that can thrive growing underneath honeysuckle.
The greatest nuisance is the vine’s ability to climb trees, which they eventually kill. The aerial vines produce fruit (red berries) that birds help spread. Wintercreeper has become established in woodland areas throughout Clark County, and one can spot many of these “Euonymus trees” in Winchester. Sadly, the plant is still being sold and planted.
Warnings not to plant invasive species should be taken seriously. Go native!
