Our predecessors thought they were doing a good thing by introducing certain plants to properties. They were looking for solutions to problems such as erosion and keeping wildlife from eating crops. They needed something that would grow fast and cover a lot of ground.
Fast-forward a few years and what we now call ground cover are possibly aggressive or invasive plants that are taking over lawns, fields and forests. Two examples are crown vetch and multiflora rose.
Crown vetch (Coronilla varia) also known as ax seed, ax wort, hive vine or trailing crown vetch, was brought here from Europe in the 1950s. It was, and still is, being used as a ground cover to help prevent erosion.
It is a low growing plant with a creeping stem that grows to less than 2 feet and pink to lavender and white flowers that bloom from June to September. It is a member of the legume (Papilionaceae) family. Other family members include sweet pea, green bean, Texas bluebonnet and wisteria.
One crown vetch plant can cover 6 feet in diameter.
Once crown vetch is established, it has a high tolerance for many conditions. Preferring full sun, it will also grow in sparse shade. It grows in rocky, dry sites as well as moist areas with good drainage in USDA Zones 3-10. It spreads by rhizomes and seeds that can remain viable in the soil for years.
Crown vetch plants and seeds are poisonous when consumed by humans or horses. It grows along roadsides, often spreading into lawns and fields. Grazing animals may come into contact with it without you even realizing it may be present.
Multiflora rose (Rosa multiflora), also known as baby rose, Japanese rose and seven sisters rose, originally was introduced from Asia and was used as a living fence, to control erosion and provide food and cover for wildlife.
Multiflora rose is a climbing or rambling shrub with a single stem or, at times, multiple stems. The canes have paired, curved stout thorns. The leaves are alternate and compound and composed of five to 11 leaflets. The serrate leaflets range in size from ½ to 2 inches long and are ovate in shape with pointed tips.
The plant can grow 9 to 12 feet wide and 6 to 10 feet tall. Several hundred white or pinkish flowers bloom in clusters from May to June and will yield a small round fruit (the rose hip) that changes from green to red upon maturity. The hip contains seeds that can remain viable in the soil for 10 to 20 years! It also spreads by layering when the cane tips reach the ground and take root.
Multiflora rose is now considered a noxious weed in Pennsylvania.
Both crown vetch and multiflora rose can be managed by repeated mowing. Carefully digging out the roots works with small populations. With multiflora rose, a backhoe may be needed as there are extensive roots.
Three herbicides have been used to manage crown vetch and multiflora rose with varying success.
The best time to manage crown vetch is in the early summer when the plants are actively growing. Glyphosate, a non-selective herbicide, and 2, 4-D, a broad-leaf weed killer, will often require two or three applications. Triclopyr, another broad-leaf weed killer, has been successful in established stands. Always read and follow the directions on the label.
Unfortunately, these treatments to the tops of the plants do not affect the seed bank, which remains viable for years. Constant scouting is needed to prevent re-establishment.
There is a biological control called rose rosette disease, which is a native virus vectored by an eriophyid mite (Phyllocoptes fruitiphilus). The virus will attack the multiflora rose, leaving it stunted and turning it red in color, eventually killing it. However, the virus infects native as well as commercially grown roses.
Many people take advantage of herbivores. Sheep and goats have been used to eat brush and weeds. Goats, especially, are not deterred by thorns. They can stand on their hind legs to forage for food, reaching higher and debarking the canes. Make sure, however, that these herbivores are fenced in. You don’t want your hungry four-legged friends wandering over to your own or your neighbors’ flower or vegetable gardens!