Coastal Invasive Species Committee

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Periwinkle (Salt Spring Island Concervancy)

ALIEN PLANT INVADERS: PERIWINKLE

Jean Wilkinson, Stewardship Committee, Salt Spring Island Conservancy.

In the Georgia Basin, Common and Greater Periwinkle have unfortunately escaped from many gardens and spread into nearby woods and riparian areas, negatively impacting local plant communities and habitats.

This Eurasian import has long been popular as an evergreen groundcover because it grows rapidly, has attractive blossoms, and tolerates a wide range of conditions. Some garden columnists claim periwinkle allows other plants to survive and grow through it, but in this region (and many other parts of the world) it becomes a dense monoculture if left unchecked. Some jurisdictions have banned it, and some BC nurseries no longer carry periwinkle due to its invasive nature.

Because it tends to overrun garden beds, excess plants are often thrown onto compost piles and into natural areas, where periwinkle poses a serious threat. New colonies can grow from small plant fragments, forming thick mats that choke out native plants, prevent re-generation of trees and shrubs, and diminish local biodiversity.

Everyone can help reduce the negative impacts of invasive species by controlling infestations. Check the wooded areas and edges of your property as periwinkle (or other alien plants) may be invading from your neighbour's lot. If you grow periwinkle, please ensure that it doesn't spread to wild spaces by planting it in an area contained by concrete or similar barrier, and use extra caution when disposing of cuttings. Carefully consider how it could spread if you were to move from the property, and resist the impulse to give plants away.

Periwinkle can be removed quite easily when the ground is damp (see below), and spring is the best time to do this. Afterwards, plant native species or non-invasive alternatives (some suggestions below). Persistence is required, but you'll know you've helped protect native vegetation from an alien plant invader!

COMMON AND GREATER PERIWINKLE – FACTS ABOUT THESE HORTICULTURAL BULLIES:

Identification – Vinca minor and Vinca major. Perennial evergreen ground-cover with trailing, somewhat woody stems up to 2 metres long. Shiny, oval variegated or dark green leaves are opposite. Flowers have 5 petals that form a tube at the base, and are violet to blue or white. Greater Periwinkle has longer, arching stems and leaves to 5 or 6 cm; Common has smaller leaves and stems growing closer to the ground.

Impacts –out-competes other vegetation for sunlight, moisture and nutrients, and can form large dense mats, killing native plants, preventing growth of tree and shrub seedlings, and altering habitats

Found –in shady and sometimes sunny areas on slopes, along watercourses and on the forest floor, spreading from original plantings or garden refuse. Especially vigorous in damp areas, but can survive very dry periods.

Spreads – stems root easily wherever a node or joint touches the ground; occasionally plants also produce viable seeds

Control – Focus first on removing patches adjacent to or invading natural areas. Cut plants during active growth in early to late spring. Pulling or mowing the vines will control their spread but may result in abundant re-growth; repeated cutting will eventually kill the plant. For best control dig out the roots, but be careful not to loosen soil too much, especially near streams. Stem and root fragments will resprout, so regularly monitor the area and repeat treatment as necessary.

Disposal – Take to landfill. Or dampen all plant parts, put into heavy black plastic bags, seal, place in hot sunny spot, and turn occasionally til plants rot and turn to mush. Once absolutely dead, contents can be put into compost pile.

Alternatives –(Grows in *Sun, +Part Shade or #Full shade, M prefers Moist soil, D prefers Dry, DT is Drought Tolerant) : Native: Wild Ginger +# M; Piggy-back Plant + M; Coastal Strawberry *+ D; Kinnikinnick *+ D;

Wood Sorrel +# M; Evergreen Violet +# M,DT; Small-flowered Alumroot *+# M,DT

Non-Invasive Non-native: Christmas Box or Sweet Box (Sarcococca hookeriana)*+# M, D

More Info: Salt Spring Island Conservancy Stewardship Committee 250-537-4877, Coastal Invasive Plant Committee www.coastalinvasiveplants.com , Invasive Plant Council of B.C. www.invasiveplantcouncilbc.ca