By Lori Rose
Over the past few years, I have noticed a sprinkling of what looked like young Bradford pear (Pyrus calleryana) trees appearing along the roadsides here in Bucks County. “How cute,” I thought, “baby Bradford pears!” Everyone has seen this tree – it is the big teardrop-shaped tree that has been planted as a street tree in neighborhoods, as sentinels flanking long driveways, and as a specimen tree in lawns. In the 1980s it was the second most popular tree in the country. When they are in flower in early April, when we are in such desperate need of a taste of spring, they really are a remarkable sight.
Also known as the Callery pear, the Bradford pear tree originally had sterile fruit, meaning it would not produce seedlings. But, according to the Pennsylvania Department of Conservation and Natural Resources (DCNR), more recent cultivars were created to resist splitting by wind and snow. These trees were able to cross pollinate and produce viable seeds that are spread by wildlife. It also spreads vegetatively, with new trees sprouting from the roots of an older tree. These trees will tolerate a wide variety of conditions – sun or shade, wet or dry – and the cute little seedlings have now spread and become veritable thickets. We are just beginning to see this invasion here in Pennsylvania, but Virginia and Maryland have been dealing with it for some time.
This past spring, when the flowers bloomed, I was awestruck by just how many of these thickets there are. It seems like just this year the youngsters of the landscape trees planted 10-20 years ago have taken over our native greenways, including a small patch of woods in my own back yard. As much as I enjoyed them over the past few years, this April, while they were flowering and easily identifiable, I cut them all down in hopes that some of the native trees would reclaim their habitat. Since the Bradford pear will resprout from a cut stump, the DCNR suggests treating stumps with an herbicide such as glyphosate. And since glyphosate is not environmentally friendly, I used a paintbrush to apply it to my stumps to ensure that it did not inadvertently land on the soil or any other nearby plants.
As I was researching the Bradford pear tree, I noticed many other trees and shrubs on the DCNR’s list of invasive species that have been landscape staples for decades. You may recognize them too. The recommendations for eliminating them from our local environment are the same as for the Bradford pear–remove them, root and all, and if that is not possible, cut them down and apply an herbicide to the stump. Here is a list of some of the most common invasive species used in landscape plantings:
Butterfly bush (Buddleja davidii), or summer lilac, was brought to the U.S. in the early 1900s as an ornamental shrub from its native China. Its long spikes of fragrant purple flowers are very attractive to butterflies, and the flower clusters become heavy enough to make the branches bend, giving the shrub a pretty weeping silhouette. The thousands of tiny seeds spread far and wide, and will grow in poor, dry soil where many native plants will not survive, such as along roadsides and train tracks. It also grows well in wet areas, invading stream and riverbanks and forest edges. The DCNR says because this shrub has been planted so extensively, it commonly escapes into a variety of habitats where it displaces native plants. Instead of butterfly bush, try planting blazing star (Liatris spicata), summersweet (Clethra alnifolia), or butterfly weed (Asclepias tuberosa).
Burning bush (Euonymus alatus), or winged euonymus, was introduced into the United States in 1860 for use as an ornamental shrub. Its gorgeous, bright red fall foliage and neat habit has made this shrub a popular ornamental plant for landscape designers. Because of this, and because it grows quickly, it is commonly planted along interstate highways, as hedges and in foundation plantings. They are so pretty it is hard to reconcile cutting them down, but according to the DCNR, the burning bush gets so large and dense it easily outcompetes native plants. Lacking pests and tolerant of deep shade, this shrub can force itself into moist forested sites, creating large thickets that displace native herbs and shrubs. Some native alternatives include witch-hazel (Hamamelis), common winterberry (Ilex verticillata), and Virginia sweetspire (itea virginica).
Here in Pennsylvania we have both versions of the invasive periwinkle vine, Vinca major and Vinca minor. They look and act very similarly, trailing along the ground with pretty pinwheel-shaped pale purple flowers in late spring, with evergreen leaves that are sometimes all green and sometimes green edged with white. It was brought over from Europe in the 1700s as an ornamental ground cover and is still sold in nurseries today. Please do not buy it if you see it for sale. The DCNR says this plant can form thick mats and extensive infestations under even dense, dark canopies. It has the ability to take over an understory, removing habitat for native vegetation. Try the native evergreen partridge berry (Mitchella repens) instead. It has pretty, fragrant star-shaped white flowers that glow in the late-spring shade, followed by bright red berries in summer and fall.
We all know and love that harbinger of summer, like fireworks, the orange daylily (Hemerocallis fulva). It is an easy plant to hybridize, and there are thousands of cultivars, but the original orange daylily is unfortunately invasive. A very popular ornamental, prized by gardeners for its hardiness and versatility, it was introduced from Asia into the United States in the late 19th century. The DCNR says that once established, orange day-lily spreads to form dense patches that displace native plants. Its thick tubers, which are buried under a dense mat of its own vegetation, make orange daylily a challenge to control. Gardeners often inadvertently spread orange daylily to new locations when throwing away whole plants. This last sentence made me laugh – I always joked that you can throw an orange daylily into a ditch upside down and it will still thrive. Dig them up, throw them on the compost heap or in the trash, and replace them with one of the many sterile and more demure cultivars.
Japanese pachysandra (Pachysandra terminalis), or Japanese spurge, is an evergreen perennial groundcover brought to the U.S. from eastern Asia. It spreads quickly through underground stems and roots, and easily escapes from cultivation, colonizing forests and meadow edges. It tolerates sun, loves partial shade, and will even grow in deep shade, forming dense mats that suffocate native species and, according to the DCNR, provides little benefit to wildlife. Instead of pachysandra, try creeping phlox (Phlox subulata), wild ginger (Asarum canadense), or foamflower (Tiarella cordifolia).
I am heartbroken. I have all of these plants in my yard or garden. It will take some effort, and I will grieve for my old garden friends, but I will do the right thing and remove them. I hope you will do the same, and encourage others to do so as well. Then let’s replace them with some of these suggested native plants, and make some new garden friends.
Lori Rose, the Midnight Gardener, is a Temple University Certified Master Home Gardener and member of GardenComm: Garden Communicators International. She has gardened since childhood, and has been writing about gardening for over twenty years.