American Pennyroyal - Another Native Groundcover

While it may be a little late in the season to talk about starting annuals from seed, but I thought American Pennyroyal was worth mentioning here. It is a tough little plant that grows in dry, partly shady locations and is quick and easy to germinate.  It has a low-growing (6-12”) and spreading habit qualifies it as a native groundcover.

American Pennyroyal, Hedeoma pulegioides, is a low growing herb of the mint family that has been used extensively by both Native Americans and the colonists for its medicinal properties. Medicinal uses include treatment for colds and fevers, as a gastrointestinal aid (‘warming to the stomach’), and as flavoring agent in foods, like tea and ice cream. The colonists readily accepted this herb as a replacement for the European or English pennyroyal (Mentha pulegium) that they were accustomed to using. The plant is rich in a pungent, volatile oils including pulegone (whence the species name), which holds most of the medicinal properties; however, large doses are reportedly lethal. For the hikers, rubbing the leaves on your skin repels mosquitos and other biting insects.

The plant grows in dry upland woods and can occur as rather dense colonies. In nature, it is often found growing in openings in the woods and along paths. The native range runs all along the East Coast (except Florida) and west to Oklahoma and North Dakota.
Small blue tubular flowers are borne in the leaf axils of the erect stems from July to September. While the flowers do attract some tiny insects, they are difficult to see unless you get down on your hands and knees.

The real garden value of this plant is in its aromatic character and its ability to grow thickly in dry partly shady conditions. I am putting it along walkways so that you get a burst of the minty aroma anytime it is disturbed, or stepped on. I started my first ‘crop’ in 2009, with seed from Companion Plants, and am seeing new colonies springing up in adjacent areas. It is easy to distinguish from other sprouts, because as soon as you touch it you get a whiff of its minty aroma. This is a good example of what I am looking for in a native annual, that is, an annual plant that is able to persist on its own without my direct involvement and has desirable garden traits. In the case of American Pennyroyal those are its stimulating aroma and ability to grow in dry partly shady locations. 

Native Ground Covers

When it comes to landscaping around the home, many people seem to be more comfortable with a single carpet-like planting – grass, vinca, or pachysandra. This is more comforting, easier to ‘read’ and may be a representation of nature ‘controlled’.  In the natural world the ground cover layer is more likely to be a mix of species. Each species occupies a preferred niche in both time and space. Hayscented fern is one of the few species that I’ve seen that can really appears to dominate a space, but that was in a recently cleared forest. On closer examination other species were present at ground level. With time a more diverse community will develop.

In designing a ground cover planting with native species you should draw on a palette of low-growing plants that can work together and are appropriate to the site conditions. While the following list is not exhaustive, these are some of the natives that I have grown around my home that work well as ground covers.



Black Huckleberry, Gaylassacia baccata, is and evergreen woody subshrub that is found in upland woods and handles a range of soil moistures, wet to dry, and sun exposures light shade to full sun. It grows 1-2’ tall and twice as wide. I was impressed by the glossy green (and a few bright red) leaves in February. The flowers develop slowly through the spring and are just now opening. I’m looking forward to larger plants so that I can see these colorful flowers without bending over so much. Although slow growing, I have been able to grow this plant in a variety of difficult locations. This plant is becoming more available in the retail trade. Other huckleberries, preferring moister conditions, are also available.

3-Toothed Cinquefoil, Sibbaldiopsis tridentata, (formerly of the genus Potentilla) is another tough plant for tough conditions. I’ve seen this growing at the top of Cadillac Mountain in Acadia National Park. I’ve had a good experience growing this plant in a variety of challenging locations, such as on the edge of yew bushes. With a little protection it is evergreen through the winter and it produces clusters of white flowers in summer. While it can form a dense mat, it is not so thick as to exclude other plant from growing with it.


Bearberry, Arctostaphylos uva-ursi , grows under what would be considered very harsh conditions, but is must have very well drained soil to survive. While I’ve encountered it growing out of cracks in boulders on a hiking trail, I haven’t had much luck with this plant on my ‘typical’ residential site (too moisture retentive, my guess); therefore no photos, either.

Barren Strawberry, Waldsteinia fraganoidies, formes a fairly dense evergreen mat with good weed suppressive character. It produces yellow flowers in early spring (now in New England), but the fruit is inedible. In the photo it is growing with sensitive fern and Mayapple.  This native can be found at some nurseries, but its cousin, Siberian Barren Strawberry, Waldsteinia ternata, is much more available and is often sold under the same common name.

Hairy Alumroot, Heuchera villosa, has been a very effective ground cover for me in partly sunny locations. The collection shown here was grown from seed which produced a mixture of green and purple leaf forms. The leaves cast enough shade to control weed growth from below. Later in the summer it produces small white flowers on long racemes, but these are not particularly showy compared to many of the Heuchera cultivars.



Some other native plants that I have been trying around my home, which can be used in a ground cover mix, include Partridgeberry (Mitchella repens), Wintergreen (Gaultheria procumbens), Canada Mayflower (Maianthemum canadense) and Virginia Creeper (Parthenocissus quinquefolia) and a variety of ferns. There are many more native species that can be used as ground covers. Just take a walk in the woods to see what’s growing there. What other natives have you used as ground covers?

For more information on native groundcovers, check out this article from the Brooklyn Botanic Garden.  Also, check out my follow-up post Native Ground Covers - Part 2.