Vinca

Two plants, one name, and one of them is invasive

Ask for vinca at a garden center in May and you will be shown a tray of annual bedding plants with glossy leaves and flat pink or white flowers. That is Catharanthus roseus, sometimes called Madagascar periwinkle or annual vinca, and it is not a Vinca at all.

This entry covers Vinca minor, common periwinkle, the evergreen creeping groundcover with small blue-lavender flowers that is sold in flats for planting under trees and on banks.

The distinction matters for one reason above all others. NC State classifies Vinca minor as an invasive species by the NC Invasive Plant Council. The annual bedding plant carries no such listing.

The two vincas, side by side

Since the whole of this page depends on knowing which plant you have, it is worth setting the two out together. They are in different genera, they are bought for different jobs, and only one of them is the problem.

The short version: if it flowers all summer in full sun and dies in autumn, it is annual vinca and there is nothing to worry about. If it is an evergreen mat under trees that flowers briefly in spring, it is Vinca minor, and the rest of this page applies.

Why it is listed

NC State describes a creeping, spreading habit with a rapid growth rate and the ability to root at the nodes, enabling it to form a dense mat over a wide area.

That sentence is the whole problem. A stem that roots wherever it touches soil does not spread outward from a clump, it advances continuously, and every fragment left behind after weeding starts again.

In a garden bed that makes it an effective groundcover. In woodland it makes a permanent mat that excludes spring wildflowers and tree seedlings, and it is thrown over the boundary in garden waste, which is how most infestations begin.

The honest position: it is a genuinely useful plant in a hard, contained situation, and a bad choice anywhere it can reach woodland or a stream. Where it is already established over a large area, removal is a multi-year job.

What it does well

Hardy in zones 4a to 9b, growing 3 to 6 inches tall and 6 to 18 inches wide, spaced under 12 inches apart.

Its real strength is light tolerance: NC State lists full sun, partial shade, dappled sunlight and nearly full shade. Very few flowering evergreens cover ground in near-full shade, which is exactly why it keeps being planted under trees.

Soil can be clay, loam, sand or high organic matter, preferring moist ground with good drainage and tolerating occasional dryness.

Flowering is small blue-lavender five-lobed tubes under an inch across, mainly spring and early summer but intermittently through the year.

If you are planting it anyway

1. Check your state first

   Invasive listings are regional. Where it is listed, choosing something else is the straightforward answer.

2. Contain it physically

   A hard edge it cannot root past: paving, a mown strip, a deep edging board. Nothing else stops a plant that roots at every node.

3. Never put clippings in the green waste heap

   Fragments root. This is the main way it escapes gardens, and it is entirely avoidable.

4. Keep it away from woodland edges and water

   Those are the habitats where it does real damage, and where recovery takes years.

5. Watch for stem canker

   Vine stem canker, or blight, can damage or kill large patches, which is unnerving in a plant grown specifically for uniform cover.

What to plant instead

For dry shade under trees, which is the job vinca is usually asked to do, the alternatives that actually work include native sedges, wild ginger, foamflower, Pennsylvania sedge and creeping phlox depending on region.

They are slower to cover, which is the real trade. Vinca’s appeal is that it fills a difficult area quickly, and the reason it is listed as invasive is exactly the same trait.

What goes wrong

NC State’s problem list is short: the orange-shouldered sherbet moth among insects, and vine stem canker, which can damage or kill large patches.

Canker showing as dying patches in an otherwise dense mat is the one complaint people actually report, and it tends to appear where the mat is thick, wet and airless.

Annual vinca, and the one disease that matters

Annual vinca is described by Clemson as one of the most trouble-free bedding plants there is, with one qualification that accounts for nearly every failure.

Phytophthora root and stem rot is the problem, and it follows wet ground rather than neglect. This is a plant from a hot dry climate, and it fails in cool wet springs, in heavy soil, and where it is watered on a schedule rather than when it needs it. The symptoms are stem rot at the base, foliar dieback and sudden collapse of individual plants in an otherwise healthy bed.

• Do not plant it out early. Annual vinca set into cold wet soil in spring is the classic way to lose it. Wait until the ground is genuinely warm, later than you would plant most bedding.
• Drainage over everything. Raised beds and containers suit it better than heavy ground.
• Buy a resistant series. The Cora XDR series carries resistance to multiple strains of phytophthora root rot, which is a real difference rather than a marketing line, and it is the sensible choice on any site that has lost vinca before.
• Do not replant vinca in the same spot after a collapse, because the organism persists in the soil.

Beyond that, the modern series differ mainly in size and heat tolerance rather than in care: Cora and Titan run 12 to 16 inches, Heatwave stays around 10 inches and suits containers, and Tattoo carries a watercolor-effect petal in cherry, blueberry, papaya and tangerine.

Vinca minor, and the canker in a thick mat

On the perennial side, the complaint people actually report is dying patches in an otherwise dense carpet, which is stem canker. It appears where the mat is thick, wet and airless, and that is the clue to the response: it is a density problem rather than an infection to spray.

Thin the mat where it is deepest, clear leaf litter that traps moisture on top of it, and cut out and remove the affected patch rather than composting it. On a plant this vigorous the gap closes within a season, which is the one advantage of a groundcover that spreads faster than you want.

Toxicity, in plain terms

NC State’s entry for Vinca minor carries no toxicity listing, and this page records that as not recorded rather than a confident no.

The related annual, Catharanthus roseus, is a different matter: it is the source of the vinca alkaloids used in chemotherapy, and it is listed as toxic. That is another reason the two plants are worth telling apart rather than treating as one.

Frequently asked questions

Is the vinca in bedding trays the same plant?

No. Annual bedding vinca is Catharanthus roseus, Madagascar periwinkle, a different genus. This entry is Vinca minor, the evergreen creeping groundcover, which is the one classified as invasive.

Is periwinkle invasive?

Vinca minor is classified as an invasive species by the NC Invasive Plant Council. It roots at every node and forms a dense mat that excludes woodland wildflowers, and it usually escapes through dumped garden waste.

Will it grow in full shade?

Nearly, yes, which is why it is so widely planted. NC State lists everything from full sun to nearly full shade, and very few flowering evergreens cover ground that deep in shade.

How do I get rid of it?

Slowly, and completely. Every rooted node and every fragment can regrow, so partial removal fails. Expect repeat passes across more than one season, and never compost the material.

Why are there dead patches in mine?

Most likely vine stem canker, which NC State notes can damage or kill large patches. It shows up where the mat is thick, damp and airless.