Gardeners celebrate Earth Day all year-round. We stay in harmony with the turn of the seasons and care for the patch of earth just outside our door. We know that successful and attractive gardens, like all natural environments, have successive layers of plants — from the low plants carpeting the ground, to taller perennials and shrubs, and culminating in trees.
I have been gardening at the same house in Wallingford for 30 years, and plants in my garden that started as gallon-pot size have grown to create an overstory, making by ground shady. I am revitalizing my backyard and making a list of low plants that thrive in shade.
Nature abhors a vacuum, and that is certainly true in the garden. Open ground does not exist in the wild, and if you have it in your garden, it will sprout weeds. You can choose to keep it bare by constant weeding, applying herbicides or spreading bark. I think that a garden with nothing but trees, shrubs and beauty bark is anything but attractive.
Garden complements
In selecting and placing low-growing plants, use criteria that your would use in choosing any plant. Read about its habit, either in a book or on the plant tag, and match the plant to its cultural requirements of sun exposure and water needs.
Look at the form and texture of the plant and its leaf color, then deliberately contrast those to adjacent plants, or use those elements to echo similar ones.
One example would be to use purple carpet bugle (Ajuga reptans ‘Atropurpurea’), with its bronze-tinted leaves, to repeat the mahogany winter color of Rhododendron ‘PJM.’ Add a golden plant, such as golden creeping Jenny (Lysimachia nummularia ‘Aurea’) that would complement the bronzy tones and provide a fine leaf texture. (Note: Give it shelter from the hottest sun, or it may burn.)
Another important criterion is how quickly the plant spreads. Does it root as it goes or spread by underground runners? Vigorous growers may be a good thing if you have a lot of ground to cover, but they can overwhelm other choice plants in the garden and can be difficult to control and even more difficult to remove if you change your mind in future years.
Among these are creeping St. Johnswort (Hypericum calycinum) and bishop’s weed (Aegopodium podagraria). These may be fine if you want to cover a large area, but they do not belong in a garden with a variety of perennials and small shrubs.
Read carefully about each groundcover before you let it loose in your garden.
Usually groundcovers are available in 4-inch pots, making them less expensive per plant than those in larger sizes. Plant them 1 foot apart, so they will grow in to make an even cover in a season or two.
Mixing it up
Instead of a mass planting, consider using a mix of low plants to add a tapestry at ground level, letting them interweave as they grow together.
Here are a few that I recommend you consider.
For acid conditions, perfect under rhododendrons, try inside-out flower, (Vancouveria planipetala). A Northwest native, it has tiny, white flowers on evergreen leaves.
Creeping lilyturf (Liriope spicata) brings in a grassy texture and blue flowers. It will do well under shrubs or trees and will take sun, too.
Japanese spurge (Pachysandra terminalis) is a stalwart, evergreen spreader, a little on the vigorous side, for shade. Reaching 6 inches, the glossy, dark-green leaves are topped by small, white flowers.
A new pachysandra, Pachysandra axillaris ‘Windcliff,’ has fragrant, white flowers in spring that repeat again in the autumn. It grows to 6 inches and takes shade to part-shade.
Another fragrant plant, Sweet box (Sarcococca hookeriana humilis) reaches 18 inches in height and spreads by underground runners. Its small, white flowers are very fragrant in the winter, mostly hidden in the handsome, shiny, dark-green leaves.
The queen of shady groundcovers is epimedium. I have found Epimedium pinnatum ‘Colchicum’ to be a good evergreen presence throughout the winter in my shady garden, growing 16 inches tall. Yellow flowers with short, brown sepals appear in late winter.
Many gardeners cut the leaves to the ground in March before the bloom, and new leaves emerge to renew the foliage and allow the flowers to stand out.
You will find dozens of varieties of epimedium available in the trade, varying in leaf size and flower color.
So celebrate Earth Day this year by finding space in your garden for a new groundcover plant.
PHIL WOOD is the owner of Phil Wood Garden Design in Seattle.