Creeping groundcovers can be invaluable allies in the garden: plant a few and they multiply and spread, filling the empty spaces in our flowerbeds without our having to intervene. Especially those that tolerate shade, as they sometimes grow even under other plants, acting as a living mulch. What more could a laidback gardener ask for?
Priority Invasive Exotic Plant Species
Those who are less lazy, on the other hand, may appreciate them less, since they tend to get out of hand. Some even go so far as to call these plants invasive. What an insult! For my part, I prefer to save this word for plants that are truly invasive, such as Japanese knotweed, garlic mustard or Norway maple: plants that come to us from abroad by accident or that have escaped cultivation and are causing real problems by disrupting our ecosystems and sometimes our economy. Here in Quebec, they are known as priority invasive exotic plant species (PIEFS).
However, there is a whole list of plants that are not named PIEPS, but which tend to spread, either by their rhizomes, stolons or seeds. Others could become problematic in the future, but in-depth research has yet to be carried out. And, to complicate matters further, exotic plants may be invasive in some areas, but not in others. A real mess for our readers!
Awareness and native planting
You’re probably wondering why I’m worrying you with all this and, more importantly, what to do about it. First of all, I think we need to be aware of the issue of invasive plants. Unfortunately, many nurseries still sell plants considered PIEPS in Quebec. If they are still selling invasive plants, they certainly won’t advise you on species whose status is uncertain. I’m not asking you to pull up your periwinkle carpet or Japanese pachysandra either, but keep an eye on them, especially if you live near woodlands or protected areas.
Fortunately, there’s a simple solution to this problem: plant native groundcovers! Here are 5 species of ground-covering perennials and shrubs you can use in the garden, without worrying about them running away from home. And they’re common enough that you may already have some in your home without knowing they’re native.
Canadian Wild Ginger (Asarum canadense)
Canadian wild ginger used to be found throughout the forests of eastern North America. It is now quite rare, having been harvested for its medicinal virtues. Although it produces small brown inflorescences, its main interest lies in its ability to spread its green leaves quite aggressively in the shade. Only 15 cm high, it will smother lower plants, including weeds, under a dense carpet of greenery, but will take time to establish. It’s also a very hardy perennial, surviving up to zone 1 USDA.
Bearberry (Arctostaphylos uva-ursi)
I’ve often used bearberry for curb appeal because of its salt resistance, but this creeping shrub can adapt to almost any condition, even deep shade. Native to Canada’s Far North and Greenland, it can be found as far away as New England, on the tundra, at the top of mountains, along coastlines and in forests. Its origins give it good resistance to the cold; it can grow in zone 1 or even zone 0!
Its main attraction remains its evergreen foliage, which turns bronze in winter, but it still produces an enormous number of small white flowers in spring, and fruits that delight birds (and bears, perhaps?). Rarely exceeding 40 cm in height, bearberry can still require a little vigilance, as it has a tendency to spread.
Virginia bluebells (Mertensia virginica)
Virginia bluebells are renowned for their brief but abundant spring flowering, as they live in large groups producing blue flowers on 60 cm stems. Pollinators love it, from native bees to butterflies and hummingbirds. Yet it’s a hardy perennial that adapts equally well to mountain tops and stream banks, resisting wind and snow, but above all shade, where it will produce large green carpets. Delicate as it may seem, it is hardy up to zone 1. It is found mainly in the central and eastern United States, but is native to Quebec and Ontario, where it is considered vulnerable.
American Wintergreen (Gaultheria procumbens)
This small shrub is often used in herbal teas or in the cosmetics industry for its balsamic scent. Yet it’s a champion of northern gardens, with exceptional hardiness, up to zone 1 USDA! Its small, shiny leaves are evergreen, and its creeping branches take root on contact with the ground. In spring, wintergreen produces small white bell-shaped flowers that bear fruit. In August, its red fruits are as impressive as its blossoms. It can be found in the wild from Newfoundland to Manitoba, and as far south as Alabama.
Heartleaf Foamflower (Tiarella cordifolia)
This tiarella, native to eastern North America, is already popular in our gardens and is readily available from nurseries. It’s an understory perennial, so shade-resistant, and spreads by runners. However, it is not invasive. Its heart-shaped flowers are downy and it produces feathery white flowers in spring. Hardy in zone 2 USDA, it will adapt to most gardens.
I went through quite a bit of anxiety when I didn’t have my knowledge in this area.
Great article. I was able to pick up some things at a native plant sale recently. An article your father wrote said that in true Laidback Gardener style, he shaded out horsetail. I have a heavy clay bank that I am planting with natives in an attempt to do the same thing. Perhaps I will try some American Wintergreen in the part shade areas!
Do you know of a groundcover that can stand up to light foot traffic in the paths between raised beds in Lillooet, B.C.?
some types of sedum; creeping thyme; Irish moss; ground clover; dichondra
Hi, you say you won’t recommend people pull up their periwinkle. Here is a good write up about why you SHOULD:
Here are some excellent comments from Cathy Kavassalis, a Halton Master Gardener:
“Invasive Species: Concepts and Controversies continued.
This is a follow up on the article I wrote to frame the invasive species conundrum ….Let’s look at periwinkle or myrtle (Vinca spp.) as an example. Vinca is a member of the dogbane family (Apocynaceae – known for plants that are poisonous to dogs). It is native to central and southern Europe. However, it has been spread around the globe and is a problem species from Australia to Canada, because it has jumped the proverbial garden fence.
There is no question it is a lovely evergreen plant that can grow in difficult areas. It is green; it can prevent erosion; it can reduce the need to mow. Those are good things right? Yes, but the those benefits do not outweigh the damage this plant is causing and there are alternatives.
Here are some facts about periwinkle. Vinca reproduces by stolons (runners), with stems rooting at the nodes. Small fragments are capable of starting new colonies. When gardeners discard plants (or share), just small fragments in soil can start an invasion. Seeds are not a big concern, although seeds in soils when moving other plants from place to place can contribute to its spread.
Vinca minor is evergreen and can capture sunlight in early spring and late fall and shade out other plants, particularly native species. Where dense mats form, many native understory plants begin to disappear. There is evidence that in addition to shading out competition, this species can release compounds in the soil (allelochemicals) that inhibit the growth of other native plants like sugar maple seedlings.
I won’t let it escape my garden!
So let’s assume you can keep your vinca perfectly contained and won’t share plants or discard plants carelessly. What’s the harm? What you may not be aware of is that this plant affects the life in your garden, from soil dwelling microbes to birds in the trees.
One reason Vinca is so successful is that it is mildly poisonous. It produces some 50 alkaloids, compounds evolved to reduce feeding by herbivorous animals. This limits animals and in particular insects that can live in your yard: the bees that can use the pollen, the butterflies that can develop, the birds that can feed on the insects.
One interesting study looked at spider populations around mats of periwinkle: “The vine Vinca minor promote elevated densities of Lycosid (wolf) spiders by reducing cannibalism and predation among closely related spider species .… Predator promotion can lead to myriad direct effects on herbivorous insect communities ..and co?occurring predator populations .… There are hints that the effects may even extend indirectly to affect the fecundity of neighboring plants.… The broader implications for community dynamics remain unexplored,”(Smith-Ramesh, 2016).
Now you may not care that one wolf spider species benefits over others. But what this should tell you is that our plant choices alter the species that can survive in an area. As we remove food sources, we reduce populations of native species. While vinca is visually attractive and you may be able to prevent its spread, by growing this plant you are impacting local species in ways that have unknown long term consequences.
The recent work by entomologist Doug Tallamy has shown that “Every time a species is lost from an ecosystem, that ecosystem is less able to support us.” Our landscaping choices matter.
Alternatives to periwinkle exist.
There are many alternative plants. They will be less easy to establish. Invasive species by their nature are easy to grow. But the benefits to the health of our planet are worth the effort.
The possibilities depend on location, soil and site conditions. There is no one plant fits all recommendation (if you find one, you can guess it’s likely a problem plant). A short list of ideas:
Pussytoes (Antennaria spp) • a mat-forming plant, with the leaves and flower stalks being woolly and grayish. It is best grown in lean, gritty to rocky, dry to medium moisture, well-drained soil in full sun to part shade.
Wild Bunchberry (Cornus canadensis) • a plant with beautiful white flowers that produces red berries. Stunning
Ginger (Asarum canadense) • a slow-spreading plant that does well under full shade or in a woodland setting.
Wild Strawberries (Fragaria virginiana and Fragaria vesca) • low, spreading strawberries that produce tasty small berries.
Checkerberry (Gaultheria procumbens) – for the right site only – needs moist organic, acid soils with good drainage, light to full shade cool
Dwarf Raspberry (Rubus pubescens) • a small running species of raspberry that spreads along the ground and will produce small red berries.
Barren strawberry (Waldsteinia fragarioides) • a mat-forming plant which spreads by runner-like rhizomes creeping just below the soil surface and features 5-petaled yellow flowers. It is easily grown in average, medium, well-drained soil in full sun to part shade.
Creeping juniper (Juniperus hortizonalis) • is a procumbent evergreen that adapts to a wide range of soils, but prefers a dryish, sandy soil.
More ideas:
Alternative Plants https://cvc.ca/wp-content/uploads/2011/09/11-185-invasivesalternatives-2011-list.pdf
Native Alternatives to Wintercreeper Euonymus & Other Exotic Groundcovers http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/visual-guides/native-alternatives-to-wintercreeper.aspx
Some References:
Vinca major, V. minor Fire Effects Information System (FEIS) https://www.fs.fed.us/database/feis/plants/vine/vinspp/all.html
Cappuccino, Naomi & Carpenter, David. (2006). Invasive exotic plants suffer less herbivory than non-invasive exotic plants. Biology letters. 1. 435-8. 10.1098/rsbl.2005.0341.
Darcy, A.J. and M.C. Burkart. 2002. Allelopathic potential of Vinca minor, an invasive exotic Plant in west Michigan forests. Bios 73: 127-132
Groves, R.H., Boden, R. & Lonsdale, W.M. 2005. Jumping the Garden Fence: Invasive Garden Plants in Australia and their environmental and agricultural impacts. CSIRO report prepared for WWF-Australia. WWF-Australia, Sydney. https://plantright.org/wp-content/uploads/2017/07/Groves-et-al2005.pdf
Smith-Ramesh, Lauren. (2016). Invasive plant alters community and ecosystem dynamics by promoting native predators. Ecology. 98. 10.1002/ecy.1688. https://www.researchgate.net/publication/312222974_Invasive_plant_alters_community_and_ecosystem_dynamics_by_promoting_native_predators “
Great post highlighting our indigenous beauties. The horticulture trade has been responsible for the introduction of many invasive species. The Canadian Coalition for Invasive Plant Regulation (CCIPR) is working to improve policies, tools and regulations to create a national plant risk assessment database, ban the sale of high-risk invasive plant species and require point-of-sale labelling to educate gardeners about invasive species.