Periwinkle, Vinca minor, is a member of the dogbane family (Apocynaceae).
Periwinkle is known to have been present in North America as early as the late 1700’s.
The plant is native to the Mediterranean region of Eurasia, where it is not considered invasive, and indeed a “slow colonizer”.
It has been introduced to North America numerous times, primarily as an ornamental for use as a groundcover in gardens.
Unfortunately, despite its known invasiveness, it continues to be found in garden centres across the country.
Other uses for periwinkle include employment as a medicinal or herbal remedy and use as an erosion control plant in the past.
Here are some distinguishing features that may help to positively identify periwinkle:
Leaves are glossy, evergreen and have a faint, white mid-vein
It has long, trailing stems that grow along the ground
Single flowers bloom along the stem
Flowers are pale blue-purple, 3 cm wide and have 5 petals
Flowers bloom from May to June
Grows well in shade and tolerates a wide range of soil types
What it does in the ecosystem
Have you ever visited Strathgartney Provincial Park? If so, you may have seen an area where a dense, low-growing monoculture of green-leafed plants with purple flowers dominates the forest floor. This is periwinkle, also called vinca.
Periwinkle is a hardy, evergreen groundcover plant that is often used in gardens for its ability to suppress weed growth.
This same capacity for suppressing weed growth unfortunately makes it a prolific invader.
If the plant escapes a garden and establishes itself in the wild, it can outcompete native groundcover species and forest understory plants, significantly altering habitats.
The habitats periwinkle prefers are, unfortunately, sensitive, high-value areas like woodlands and riparian zones.
It can invade these areas because of its growth habit (groundcover), aggressive growth, and shade tolerance.
It spreads vegetatively using stolons (runners) and rhizomes, forming dense monoculture mats that prevent native species growth and reduce local biodiversity.
As periwinkle can reproduce from root fragments, it may be difficult to control once established.
Its presence has been shown to reduce populations of native spiders.
Periwinkle is unpalatable for livestock and may reduce the grazing capacity of pasturelands where it invades.
Before selecting a control method consider:
The size of the infestation,
The amount of effort you are willing and/or able to expend.
Often, multiple control methods are used simultaneously.
Consider the local ecosystem and what other organisms or ecological processes may be affected by management.
When managing periwinkle in a sensitive environment, work carefully to minimize the disturbance to local wildlife and native vegetation.
Depending on the location and extent of spread, the most feasible method of periwinkle control may be hand-pulling the plants
This method is feasible thanks to a shallow root system.
Pulling must be done carefully, as the plant will resprout from any root fragments that are left behind.
A rake can be used to pull runners up from loose soil.
If you are in an area where not much else is growing, after removing all periwinkle parts, the area may also be covered with a thick tarp.
This tarp is used to suffocate any new growth that may arise from seeds or root fragments that were missed.
Be mindful that the tarp will also suffocate any other species found beneath it.
A thick tarp of a dark colour is best, as this will block sunlight and gas exchange most effectively.
Weigh the tarp down adequately with debris, bricks, wood chips, soil, or some other weight. You can also bury the edges of the tarp to avoid its catching the wind.
Return to the site regularly to check beneath the tarp. The tarp will need to be left in place until no live plants are found beneath it.
On your returns, manage any new growth that has popped up around or through the covering.
If the population has expanded from beneath the tarp, you may want to consider extending the tarped area.
Tarp at least three feet out from the perimeter of the infestation.
Aside from areas where periwinkle grows in monoculture, tarping can also be used where other control methods have proved unsuccessful.
Mechanical controls such as mowing are not recommended if hand-pulling is feasible.
Roots will resprout vigorously after mowing.
Any stem fragments that are spread around the area by the mower may also root at the node and resprout.
The PEIISC does not provide advice on chemical control measures at this time.
If using chemical controls, it is imperative that all local legislation and manufacturer’s instructions be followed during application.
FOLLOW-UP AND REMEDIATION
After work is completed, it is important that all equipment be cleaned thoroughly and that all plant parts are removed from boots and clothing before leaving the area.
All plant parts must be collected, bagged, and properly disposed of.
After work is completed, it is imperative that all equipment be cleaned thoroughly and that all plant parts are removed from equipment, boots, and clothing before leaving the area.
There is a significant risk of exposure to sap during cleanup, so protective equipment must be left on during this stage
All plant parts must be collected, bagged, and properly disposed of
Each time you manage the site, collect, bag, mark, and dispose of all plant parts properly.
Bag the plant material in clear plastic bags.
Mark the bags boldly with a permanent marker. Write “INVASIVE PLANT” or “PERIWINKLE” on the bags.
If you have a place away from foot and wildlife traffic, you can dry out the material, making it much easier to move.
Leave the bags open and in the sun for a week to dry.
Only do this if you can guarantee that the plant will not be spread from where it is drying
If the bags are thin, double bag them to prevent accidental dispersal later on.
Tie the bags tightly and place them in your usual residential waste collection (THE BLACK BIN)
Never place invasive plants into the compost. This may allow them to become established once they reach the heap.
Clean and remove all plant parts from any equipment, clothing, or vehicles before leaving the site to prevent spread.
Plant suitable native plants at the site to compete with any regrowth that may occur after management and begin restoring the site to its natural beauty.
Plants should be selected to suit the site’s conditions. Choose plants that thrive in the environment for the best results.
Reach out to the PEIISC for assistance with selection.