Some consider them standards. Some consider them thugs. Groundcover plants are Ground Zero for the aggressive versus invasive debate, bringing up another aspect of the “right plant/right place” refrain.
The characteristics that make a good, solid, reliable groundcover, it can be argued, are the very same traits that can push it over the edge to becoming an invasive, ruinous intruder. If it tends to spread, it fills in nicely. It also may outcompete surrounding plants.
Just a little editorial note: What grows reliably and respectfully in one region may prove destructive in another. An invasive plant in one garden may be well-behaved in another. If any of these plants — if any plant — is known to be troublesome in your area, or if it has the potential to become invasive, you know what not to do.
1. Aegopodium podagraria (snow on the mountain)
Also known as bishop’s weed or goutweed, Aegopodium podagraria is prized for its ability to cover large areas rapidly, filling in to provide a continuous mound of delicate foliage. The variegated selection (A. podagraria ‘Variegatum’) has proved to be a popular choice, with its medium green leaves outlined and occasionally splotched with cream. Oval and serrated, individual leaflets grow to about 3 inches long, and are held aloft by slender stems about 8 inches tall. This cultivar is said to be less aggressive than the straight species.
Very small, white flowers assemble in a flat-topped umbel (resembling that of carrots or parsley), and the jury’s still out on their ornamental value. Many gardeners choose to remove them when they appear in May through June, preferring the presence only of the foliage. They also can be removed to help prevent self-seeding.
Snow on the mountain is happy in a wide variety of conditions, ranging from full sun to part shade and a variety of soil types including dry to medium, but welldrained soils. It tolerates drought.
The plant can spread — and does so very quickly and tenaciously — to 1.5 feet, with the help of vigorous rhizomes. And once it’s allowed to stretch beyond its allotted space, it can be difficult to control. Attempts to pull or dig up a stray plant often prove futile, as the rhizome is strong and the stems tend to break before the entire plant can be removed.
It’s best planted in self-contained areas, with no companions, where it is allowed to create its own habitat. If planted with other perennials, it soon will overtake them and crowd out the healthiest of neighbors. Rock gardens or border areas are probably best avoided, unless they’re devoted solely to A. podagraria. If there’s an installed barrier, such as a sidewalk, patio or sunken edging, this will help to contain unwanted spread.
When planted in hot and humid climates, snow on the mountain may suffer from leaf blight. And the foliage may have a tendency to flag a bit in midsummer; mow at a high setting to revitalize the bed.
Hardy in zones 4 to 9.
Suitable alternatives: Epimedium, Gaultheria procumbens, Hosta, Podophyllum peltatum
2. Hedera helix (English ivy)
The ivy-covered cottage. The hallowed halls of ivy. Wrigley Field’s ivy-covered wall.
Hedera helix stands in folklore and in commerce as one of the most beloved of plants. To the Celts, for example, ivy stood for connection and friendships; its interweaving growth — as well as its tenacity — aptly describe long-term relationships.
If Hedera helix is planted, it’s sure to extend its reach reliably and to be a long-lasting addition to the landscape. It’s tough, it’s evergreen and it can be terribly aggressive. These all are attributes of a promising groundcover — as long as the aggressiveness can be tamed.
Used as a woody groundcover, H. helix is fast growing to about 6 to 9 inches tall; over time, it can spread to upwards of 100 feet. The plant reaches maturity if it’s allowed to climb, growing up a wall, trellis or tree, where it can reach 50 to 100 feet in height. Vertical growth will encourage the plant to flower and produce seed, which is best avoided for containment purposes. But it can be contained if consistent and vigilant maintenance is practiced.
English ivy grows in two stages, and the first — the juvenile stage — is the plant most people recognize. During its youth, H. helix produces its characteristic three- to five-lobed, thick, dark green leaves, some of which may grow to 4 or 5 inches long. (Cultivars, some of which have proved to be less aggressive than the straight species, often bear variegation in the form of lighter veining or cream to golden margins.) During the second, or adult, stage, the plant is a shrubby, nonclimbing specimen that produces more ovate leaves on rootless stems. Clusters of greenish white flowers give way to dark blue berries.
The vining plant is very easily grown in average soils and can tolerate part to full shade. The stems root where the nodes touch soil; if allowed to climb, these attachments can damage painted surfaces, brick and mortar and vinyl siding.
Hedera helix is not included on the Federal Noxious Weed List developed by the USDA’s Natural Resources Conservation Service, but it does appear on the invasives lists in Oregon and Washington. Other municipalities and counties in other states are cracking down on the species, although better-behaved and well-maintained cultivars continue to be wildly popular.
Hardy in zones 4 to 9.
Suitable alternatives: Asarum caudatum; Heuchera, Mitchella repens, Pachysandra terminalis
Read More: Great Groundcover Shrubs
3. Houttuynia cordata (chameleon plant)
No wonder this groundcover is popular: It’s incredibly easy to grow, difficult to kill and it’s a standout in any garden, with its variegated and colorful, heartshaped leaves. It’s happy in both full sun and heavy shade (where its colors may not be as vibrant); it also performs remarkably well in very wet soils, and so it’s often used in ponds, bog gardens and at the margins of water gardens.
Deep, blue-green, cordate leaves (often edged with red) grow to about 3 inches long; the cultivar ‘Chameleon’ (often called ‘Variegata’ or ‘Tricolor’) features fantastically colored leaves splashed with red, pink, yellow and cream held on red stems. The variegated forms perform best in full sun. In mid- to late spring, insignificant, greenish white flowers develop; these are supported by more showy, white, petal-like bracts.
Plants tend to reach three-quarters to 1.5 feet tall, with a spread up to 2 feet.
Read more: 6 Great Groundcover Shrubs
Chameleon plant spreads by vigorous rhizomes that tend to break if they’re disturbed, making it difficult to remove the entire plant. This is a plant that, with little encouragement, shifts gear from “aggressive” to “invasive” in no time unless it’s kept in check by physical barriers. Rigid, fixed structures, such as building foundations or sidewalks, work best to limit the spread; a strong, metal edging that’s deeply sunk may also work.
In pond areas, it’s best to keep H. cordata confined to containers that are sunk into the pond bed; container walls will help to prevent the rhizomes from spreading.
This beautiful plant is nothing if not persistent, and maintenance must be routine and rigorous in order to avoid its escape.
Hardy in zones 4 to 10.
Suitable alternatives: Asarum canadense; Geranium; Brunnera, Liriope; Tiarella
4. Oenothera speciosa (evening primrose)
It’s said that if you lead someone down the primrose path, you’re luring them into a deceptively lovely life. It will be filled with pleasure but fraught with danger.
Sounds a bit like Oenothera speciosa. This lovely groundcover has its ardent fans and equally intense detractors. It has all the characteristics prized in a groundcover — it’s easily grown, it grows quickly, it spreads reliably, and it requires little maintenance. That is, unless you’ve planted it in an area where it’s likely to flex its aggressive rhizomes and spread unchecked.
Evening primrose prefers average (dry to medium moisture) soils and full sun, although it will tolerate part shade and challenging soils. It spreads both by vigorous rhizomes and through self-seeding, and it forms large colonies that have the potential to crowd out companions. Meadow sites, wildflower gardens and naturalized areas may be the best locations to plant O. speciosa.
The plant’s most outstanding ornamental characteristic is its simple, cup- or bowl-shaped, 2- to 3-inch-diameter, four-petaled, white to pink f lowers that feature yellow anthers. Blooms are fragrant, and unlike most other blooming perennials, they open in the evening and remain open until late the next morning. Flowers appear in spring and last through early to mid-summer; in some areas, blooms may last through fall.
Oenothera speciosa grows to reach 10 to 24 inches tall and spreads to 18 inches or more. Narrow, medium green leaves can reach from 1 to 3 inches long, and feature small lobes close to the base.
Hardy in zones 4 to 9.
Suitable alternatives: Helianthemum nummularium ‘Single Yellow’
5. Vinca minor (periwinkle)
If English ivy is the most common groundcover, then periwinkle must run a close second. It’s ubiquitous, used in gardens and landscapes across the country as the go-to evergreen groundcover that provides a reliable green mat as well as abundantly blooming purple (or white) flowers in spring.
Known commonly as myrtle or vinca as well as periwinkle, Vinca minor thrives in a variety of conditions, including partial sun to full shade. It does not perform well in full sun, but can tolerate a few hours without losing vigor. Evenly moist, well-drained soils are considered optimal, but the plant adapts well to average fertility and various pH levels, as well as occasional drought once it’s established.
This enthusiastic groundcover has a moderate growth to fast rate, and can be counted on to spread up to about 1.5 feet on very slender, wiry stems. If planted closely together, plants will fill in to form a nearly impenetrable mat. At most, the creeping, trailing stems reach about 6 inches tall.
Relatively small leaves — about 1 to 1.5 inches — are smooth, elliptical and medium to dark green, remaining clean throughout the year. There are a few popular varieties that offer variegated foliage, with creamy white to silvery white or yellow margins.
In early to mid-spring, single, pinwheel- like, lavender-blue flowers emerge and can remain vibrant for a few months, sometimes —sporadically — through fall. Cultivars offer a richer, red-lavender as well as white flower; mixing varieties in a planting provides a delicate blend of hues.
Vinca minor often is characterized more as “aggressive” than invasive, but if left to trail into surrounding plantings, it can outcompete fellow plants. It also can spread onto hardscape surfaces — sometimes a happy design bonus. The plant is considered invasive, however, in some natural areas, especially east of the Mississippi. As is the case with all vigorous plants, its use should be carefully considered and sited appropriately.
Hardy in zone 3
Suitable alternatives: Mitchella repens; Pachysandra terminalis, Euonymus fortunei
Read more: Good Citizen Groundcovers