(This is the seventh in a series on invasive species that inhabit the Mountain
ecosystem.)

Vinca — or known better by its common name, periwinkle — is easy to spot
on the Mountain in these winter months.

It’s a low-growing, evergreen ground cover with small, blue-purple flowers
during summer. When native plants are leafless or have died back, the
periwinkle thrives.

It forms dense mats that can shade out natives such as trillium, yellow wood
violets and tree seedlings.

“During a recent visit with a homeowner on the Salmon River I was puzzled to
not see any red alder seedlings in a large area of their property,” said Russ
Plaeger of the Sandy River Basin Watershed Council.

“Then I noticed how dense the vinca was and realized that it was preventing
the alder seeds from landing on bare ground and germinating.”

In this situation the periwinkle was interfering with natural forest processes
and preventing the establishment of trees that could help reduce erosion
problems for that landowner.

To make matters worse, during winter high water, sections of the stems of
periwinkle that are growing along a creek may break off and float
downstream. Because the plants spread primarily by runners, the pieces that
break off can take root and grow in a new location.

“Fortunately, vinca isn’t spread by seed, so unlike English ivy the birds won’t
help it move into our local forests,” Plaeger said.

“But the fact that it can readily spread along streams means vinca isn’t a good
choice for streamside zones.”

Periwinkle originated in southern Europe and northern Africa and was
introduced into the United States for use as an ornamental garden plant.

Periwinkle’s evergreen leaves are smooth, heart-shaped, 1 to 2 inches long
and are arranged opposite each other on the stems.

The flowers are found on upright stems while the non-flowering stems grow
along the ground.

The sprawling stems will root when they come in contact with the soil.
It likes moist, shady areas which makes it a threat to the riparian zones along
local streams.

This plant is an excellent example of the challenge that gardeners on the
Mountain face when bringing in a non-native plant.

Can I keep it under control or will it spread to nearby undeveloped areas.
Because periwinkle can re-root and form new plants it is best to avoid putting
them into a compost pile.

Hand pulling the vines is a good option particularly in the winter while the soil
is moist.

A rake will lift the vines off the ground for better access to the roots.

Mowing can also be effective if the area can be accessed.

At present, there are no biological controls for periwinkle.