Invasive Plants at JK Black Oak
Like most, if not all, natural areas in Northern Virginia, JK Black Oak Wildlife Sanctuary is overrun with invasive plants. If you’ve volunteered during our monthly work days, you know we spend a lot of time removing them. Why do we devote so much time to this effort?
Invasive plants are nonnative plants that are introduced (usually from another country) to areas where they do not naturally exist and cause harm. They can lead to the extinction of native plants and animals, destroy biodiversity and permanently alter habitats. In other words, invasives are a big problem. Below is a rogues’ gallery of the invasives that are most problematic at JK Black Oak.
Autumn Olive
Autumn Olive (Elaeagnus umbellata) is the most visible invasive at JK Black Oak. Not only are they large shrubs, but they are everywhere and spreading rapidly. Like many nonnative shrubs, Autumn Olive leafs out early and retains its leaves into late fall, shading out any plants trying to grow beneath it. Mature shrubs can produce up to 30 pounds of fruit each autumn, which yields about 65,000 seeds that have a high rate of germination. Birds and other wildlife eat the ripe fruits spreading the seeds in their scat. However, the sugary fruits are junk food for migrating birds who need high-fat and high-protein foods to fuel their flights.
Any attempt at cutting down Autumn Olive without applying herbicide only increases the number of stems that will sprout from its crown and roots. At JK Black Oak, we’ve been using the cut and treat method* to kill them. With the purchase of a tractor in 2023, we started cutting the shrubs down to stumps and using the tractor to pull them out of the ground. We are also experimenting with using the tractor to knock over Autumn Olive until part of the root ball is above the ground and then scoop them out using the bucket. Learn more about Autumn Olive.
Tree-of-heaven
Tree-of-heaven (Ailanthus altissima) is a very fast-growing tree that can form dense thickets. A mature female tree is estimated to produce 300,000 to 350,000 seeds that are dispersed by the wind. It’s not an easy tree to kill. Cutting down live Tree-of-heaven just creates many new trees that sprout from the roots, rather like trying to kill the mythical hydra. To make matters worse, it is also the preferred host of the invasive Spotted Lanternfly. At JK Black Oak, we started control efforts in the summer of 2024 and are using different methods to remove them. Seedlings are pulled by hand or dug. For saplings, we break the trunk and spay herbicide into the break, leaving the trunk partially attached. For the mature trees, we are trying both hack and squirt,* and a shallow, partial girdle of the trunk treated with herbicide. Learn more about Tree-of-heaven.
Bradford Pear
Bradford Pear (Pyrus calleryana ‘Bradford’) and other cultivars of ornamental Callery Pears began escaping in the 1990s (or perhaps earlier) and swept across the landscape. They have invaded pastures, forests, timbered land, hedgerows, wetlands, meadows and untended land. European Starlings (also an invasive species) are one of the primary species that eat the fruits and spread the seeds. At JK Black Oak, the highest concentrations of Bradford Pear are found on the eastern side of the sanctuary, but they are moving across the property and into the western meadow. We have started removing the trees using the cut and treat method.* Learn more about Bradford Pear.
Multiflora Rose
Multiflora Rose (Rosa multiflora) isn’t the worst invasive at JK Black Oak, but it’s the most unpleasant one to remove. The shrub’s long, thorny canes catch on skin and clothing with vicious tenacity. If not controlled, Multiflora Rose forms dense thickets by three methods: rooting at the tips of its long, arching canes, forming new crowns and canes from its spreading root system, and producing abundant fruits. Not content with smothering anything in its path on the ground, it also climbs up trees to create a tangle in the treetops.
We have tackled Multiflora Rose removal using long-handled loppers to prune it to the ground, then digging it out. Where tractor access is possible, we can bush hog them to cut back large clusters of use the bucket to scoop the entire plant out of the ground. Learn more about Multiflora Rose.
Oriental Bittersweet
Also known as Asiatic Bittersweet (Celastrus orbiculatus), this invasive vine quickly becomes a monster. It can grow to 4 inches or more in diameter and scale trees up to 60 feet high, strangling and toppling the trees. Its seed are spread with the help of birds who eat the fruit and people who cut the attractive berry-laden vines for decorations. The seeds require little light to germinate and grow rapidly, as all invasives do. The vine also spreads underground by root suckers, and its branches can root at their tips along the ground, forming tangle that smothers low-growing plants.
The forest floor at JK Black Oak has plenty of young Oriental Bittersweet. When the vines are small, they can be difficult to identify at first glance because they have an upright form that looks more like a tree seedling. However, once you pull it out of the ground and see the bright orange roots, identification is easy. Learn more about Oriental Bittersweet.
Japanese Honeysuckle
Our efforts to control Japanese Honeysuckle (Lonicera japonica) at JK Black Oak have been limited due to other invasives having higher priority. We’ve removed it from the deer exclosure fences and tree cages and have slowed its growth in open areas by mowing.
Japanese Honeysuckle is semi-evergreen vine keeps growing throughout most of the year in Virginia, which gives it a major advantage over native plants. It grows by climbing over shrubs and trees and by spreading and rooting along the ground. It can form dense thickets especially in sunny areas. Learn more about Japanese Honeysuckle.
Wavyleaf Basketgrass
Wavyleaf Basketgrass (Oplismenus undulatifoius) is a recent arrival to Virginia. It was first spotted in 2005 in Shenandoah National Park. Of all of the invasives we have at JK Black Oak, Wavyleaf may be the only one that we have a good chance of controlling. Completely irradicating it is not possible, but since we began removing it in 2022, we’ve seen a significant reduction in the number of plants. Wavyleaf Basketgrass is a very aggressive perennial grass found in forested areas that will even grow in deep shade. It creates a dense carpet of vegetation by creeping along the ground and rooting at the stem nodes. It begins to set seed in mid-August at JK Black Oak. The seeds have long, pointed tips (awls) with a sticky substance that grab onto passing animals, people, and equipment and can be carried great distances until they drop off in a new location. Learn more about Wavyleaf Basketgrass.
*Hack and Squirt: make cuts with a hatchet into the trunk at about waist height, leaving 2 inches between cuts. Spray a concentrated herbicide into the cuts immediately. Cut and treat: cut the trunk near the ground then immediately paint the stump with concentrated herbicide.
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