Anne Larson is a Des Moines-area horticulturist, certified landscape professional and-rain garden designer. She is general manager for Garden’s Grace, Inc., a metro Des Moines garden firm.

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Ground Cover
by Anne Larson       #Feature


Ground covers offer flow to landscape designs, such as this hillside garden designed as a welcome mat at the entrance of the property. Creeping phlox (P. stolonifera), lower right, gives way to Japanese blood grass (Imperata cylindrica), Daubs Frosted juniper (Juniperus  x pfitzeriana ‘Daub’s Frosted’), Pulmonaria and Jacob’s ladder (Polemonium reptans ‘Stairway to Heaven’) under the Japanese maple.

For every garden star, there is a supporting cast, and in most Midwestern gardens, ground covers perform the task admirably. Like their theatrical counterparts, ground covers’ roles may be understated, subtle and sometimes nearly invisible. Take them away and they would be sorely missed.

Ground cover plants are low-growing perennials and shrubs that do just that — cover ground — but also act as foils and accents for taller plants. They are used to transition from one area to the next, hold soil and mulch in place and offer a low-growing, low-maintenance alternative to turf.

A Sampler of Roles

Vigorous spreaders such as golden moneywort (Lysimachia nummularia ‘Aurea’) and sedum Angelina stonecrop (Sedum rupestre ‘Angelina’) are easy solutions for quickly covering erosion-prone slopes. Gro-Low fragrant sumac (Rhus aromatica ‘Gro-Low’) is a low-growing shrub that can accomplish the same thing, with prostrate branches that will sucker and form a thicket, eventually reaching 6 to 8 feet wide. The roots of these plants help keep the soil in place, thus reducing soil and mulch movement.

Many ground covers, such as spotted deadnettle (Lamium maculatum), alpine lady’s mantle (Alchemilla alpina) and the perennial big-root cranesbill (Geranium macrorrhizum), serve to soften and naturalize the edges of pathways and walls. Borders along streets and sidewalks are often prone to exposure to salt during winter months, and fragrant sumac and blue rug juniper (Juniperus horizontalis ‘Wiltonii’) are two ground covers that will hold up beautifully under these conditions.

Plants with white or golden foliage, such as the golden moneywort, ‘Caramel’ coral bells (Heuchera ‘Caramel’) and spotted deadnettle, can light up shady patches and offer a background for hosta, rhododendron and other shade-loving plants to shine. These lighter colored plants can also be a delight for gardeners who enjoy their gardens in the late afternoon and nighttime, casting a soft glow from night lighting or moonlight.

Several ground covers offer interest during multiple seasons. Fragrant sumac turns a pleasing muted red in the fall, and Angelina or stonecrop’s gold deepens to coral and orange tones as cooler temperatures approach. Coral bells, many low-growing sedum and perennial geranium maintain their foliage interest during winter months. Fragrant sumac also holds the snow artfully on its mounted branch structure.


Golden moneywort ascades down this gentle slope, forming a river of gold that offsets the burgundy foliage of the Japanese maple (Acer palmatum) and dark green of mugo pine (Pinus mugo). Note how the foliage drips off the limestone wall.

These coral bells will eventually knit together, providing a gentle patchwork of color underlying the bottlebrush buckeye (Aesculus praviflora). The coral bell closest to the hosta is ‘Caramel’. All prefer part to full shade and moderate moisture.

Establishment

There are some issues to consider when planting ground covers to ensure success. Bed preparation is key:

  • Make sure to remove weeds.
  • Lightly cultivating the soil also helps ensure success, making it easier for roots to establish themselves. Since most perennial ground covers have shallow root zones, deep tillage isn’t usually needed.
  • Place plants closer together to speed up filling in, which aids in reducing open spaces where weeds can more easily take root. Once established, ground covers tend to shade the ground and can out-compete many weeds. Removing fallen seeds from maple (Acer spp.), oak (Quercus spp.) and redbud (Cercis canadensis) is recommended.
  • Many ground covers will benefit from a light mulching at establishment to reduce soil splashing during watering and rain as well as maintaining soil moisture in the root zone.
  • A light application of a slow-release fertilizer also helps establish the plants. Apply according to label directions.

‘Gro-Low’ fragrant sumac is a strong performer in holding steep slopes, such as the 60 percent slope pictured here. And, because of its tough saline tolerance, it will handle salt splash during the winter without missing a beat.

The three-lobed foliage of fragrant sumac is glossy, turning a pleasing soft red in fall. The foliage, when crushed, gives off a sweet, musky smell that is unpleasant to deer and other mammals.

Maintenance

Woody ground covers such as ‘Gro-Low’ fragrant sumac can be trimmed periodically to maintain height. Others, such as blue rug juniper, naturally hug the ground at about 6 inches and won’t need much pruning. These and other shrubby ground covers can be contained by trimming back the perimeters.

Perennial ground covers need little to no maintenance other than cutting back discolored foliage in the spring. Coral bells and perennial geranium have crowns that sit above the soil line, so trimming above the crown is important to avoid damage to the plant. Low growers, such as golden moneywort and wild ginger, can be rejuvenated by lightly raking out dead foliage.

Ground covers that bloom in spring, such asspotted deadnettle and geranium, can be lightly trimmed after bloom to remove spent seedheads. Spotted deadnettle will often continue to bloom through put the season. Ground covers that spread from rhizomes can usually be contained in a desired area by simply digging clumps and transplanting them back into bare areas in the cover, or discarding.

A light fertilization with a slow-release fertilizer and use of a pre-emergent weed control should help ground covers get off to a good start each season. Read labels carefully, as some pre-emergent controls can inhibit root growth, such as corn gluten-based products.

Ground cover plants are short but mighty. They solve erosion and maintenance problems, tie garden areas together in pleasing ways and serve as background players to taller, more prominent garden plants. Give these and other ground covers a look — they may be waiting to be cast in an important role in your garden!

Low-growing woody plants as well as perennials can be used as ground cover plantings. Here are some suggestions for ground cover plants to use in Upper Midwest gardens:

Alchemilla alpina — (Zones 3-9) A miniature version of the familiar lady’s mantle, this petite performer sports a silver highlight on each leaf edge.

Asaram canadense — (Zones 4-6) Wild ginger is a woodland native that performs nicely in the shade as a carefree spreader.

Geranium macrorrhizum — (Zone 3-8) Ranging from white to pink blooms in early spring, this ground cover also has a spicy apple aroma unpleasant to garden pests.

Heuchera ‘Caramel’ —(Zone 4-8) The golden foliage on this coral bell contrasts nicely with its peachy plum underside.

Lamium maculatum — (Zone 2-9) Popular cultivars ‘White Nancy’ and Pink Chablis (‘Checkin’) deadnettle have silvery foliage that illuminate the shade. Some areas, especially in the Northeast, have found this to be an invasive plant.

Lysimachia nummularia ‘Aurea’ (Zone 3-9) Golden moneywort loves some moisture, and performs best in partial sun or shade.

Rhus aromatica — (Zone 3-9) ‘Gro-Low’ fragrant sumac grows 1 to 2 feet tall and colonizes hillsides quite successfully, making it great for controlling soil erosion.

Sedum rupestre ‘Angelina’ (Zone 3-8) ‘Angelina’ is an easygoing ground cover that will retain some of its gold and peachy highlights even through winter.

From State-by-State Gardening November/December 2013. Photos by Anne Larson.

 

Posted: 06/04/14   RSS | Print

 

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