Contributor: Jil Swearingen, Invasive Species Consultant, jilswearingen@gmail.com
While there are a number of native evergreen groundcovers in Maryland, you’re likely to see large patches of non-native evergreen plants covering the ground this time of year in our parks and natural areas. Most common among these are English ivy (Hedera helix), winter creeper (Euonymus fortunei), ground ivy (Glechoma hederacea), Japanese honeysuckle (Lonicera japonica), Japanese spurge (Pachysandra terminalis), and two species of Vinca – common periwinkle (Vinca minor) and bigleaf periwinkle (Vinca major). Because periwinkle is conspicuous in the winter and is known to be invasive in Maryland and other states, the Maryland Invasive Species Council has selected Vinca as the January Invader of the Month.
Common and bigleaf periwinkle are members of the dogbane family (Apocynaceae) and are native to Europe and western Asia. They were introduced to North America in the 1700s as ornamental plants and are still commercially available. Vinca is popular for residential and commercial landscape use due to its easy maintenance, hardiness, vigorous growth and general lack of pest insects and diseases. Periwinkles also have attractive pale blue, violet or white flowers and dark green or green and white variegated leaves.
Periwinkle has escaped cultivation and is invading natural areas throughout the eastern U.S. It inhabits open to shady sites including forests and often escapes from old homesites. Like other non-native creepers, Vinca sprawls across the ground, forming large patches that blanket the Earth, pushing out native herbaceous and woody species. Additionally, periwinkle impedes forest succession by preventing tree seedling survival. Once established, these invaders become year-round residents and continue to spread unchecked. Vinca spreads by vegetative means through rhizomes and fragments that can root and form new plants.
Identification
Common periwinkle and bigleaf periwinkle are easy to identify and distinguish from native and non-native species. Plants are erect or trailing, mostly evergreen with slender stems. Leaves are opposite, dark green, glossy, and oval to lance-shaped (V. minor), more rounded oval (V. major) and some cultivars have variegated leaves. Flowers are blue, lavender or white, about 1 inch across, with five petals that are widest and blunt at the tip, forming a pinwheel. Flowering occurs in the spring and can last for many weeks. Fruits and seeds are not typically produced.
Common Periwinkle (Vinca minor)
Bigleaf Periwinkle (Vinca major)
Prevention and Control
The best way to prevent periwinkle from invading our ecosystems is to not purchase or plant it. Periwinkle can be pulled by hand, dug up or raked up, but be sure to remove underground portions. Where appropriate, mowing can be used to cut plants back although this approach will likely have to be repeated regularly and may encourage more growth. Another option is treatment of foliage using a systemic herbicide such as glyphosate, with a nonionic surfactant (e.g., Kinetic) that enhances spreading and foliar absorption of the herbicide. When using herbicides and surfactants, you must follow all pesticide label directions to ensure personal and environmental safety and treatment efficacy.
Disposal
To avoid environmental harm please dispose of non-native plant materials properly. Vinca that is pulled up should be bagged and disposed of in a landfill along with other trash, put into a black plastic bag to cook in the sun until it rots, or piled up in one spot and left to dehydrate and rot.
Native Alternatives
The following native groundcovers can be used as alternatives to invasive evergreen species in landscapes in Maryland. Ideally, native plants should be purchased from nurseries that grow them from local seed or local plant stock. They should be planted in the ecological regions (e.g., Coastal Plain, Piedmont, etc.) they are adapted to and grown in the soil, light and moisture conditions appropriate for each species.
- Ferns such as Christmas fern (Polystichum acrostichoides) and marginal woodfern (Dryopteris marginalis)
- Sedges such as Pennsylvania sedge (Carex pensylvanica), blue wood sedge (Carex glaucodea) and eastern star sedge (Carex radiata)
- Perennials such as golden ragwort (Packera aurea aka Senecio aureus), plantain-leaved pussytoes (Antennaria plantaginifolia), field pussytoes (Antennaria neglecta), American alumroot (Heuchera americana), woodland stonecrop (Sedum ternatum), barren strawberry (Waldsteinia fragarioides), green-and-gold (Chrysogonum virginianum var. virginianum), partridge-berry (Mitchella repens) and striped wintergreen (Chimaphila maculata). The latter two are slow-growing and require acidic soils.
- While club mosses (lycopods) are fantastic candidates for groundcovers, they have not been successfully grown in nurseries. They should not be collected from the wild.
Look-a-likes
With their opposite, evergreen leaves, Vinca may be confused with Japanese honeysuckle (Lonicera japonica) and winter creeper (Euonymus fortunei), both long established invasive species in Maryland. You can learn more about them from Invader of the Month releases on the MISC website archives.