Ground covers are an alternative to grass. They prevent soil erosion, control weeds and provide a visual backdrop for other garden elements. Although they are often chosen for their foliage color, many gardeners plant ground covers for their attractive flowers. There are plenty of blue flowering ground cover plants from which to choose.
Any plant that grows vigorously in local conditions can be planted as a ground cover, in sizes ranging from tiny creepers to small shrubs; generally, they are less than 24 inches tall. Most ground covers are perennial plants that require very little care and grow so densely that they squeeze out invasive weeds. Ideally they will propagate and spread by themselves. Some ground cover plants can tolerate foot traffic, while others cannot.
Choosing a Ground Cover
A successful ground cover will have to grow luxuriantly in the designated site, so it must be suited to the conditions there. The plant's needs for sun or shade, wet or dry conditions, and acidic or alkaline soil must be considered, as well as its tolerance for cold and hot weather. The size of the ground cover should be suitable for the amount of space to be covered, with tall, wide plants placed in large areas only. The foliage should be attractive, because no ground cover blooms all year.
In the Sun
Campanula, called bellflower or Canterbury bells, has several cultivars. Campanula Portenschlagiana grows 6- to 9-inches tall and is hardy in USDA zones three to eight. This Dalmation native has light blue flowers in late spring. Campanula Poscharskyana is also hardy in zones three to eight and has blue flowers in summer. Its stems grow up to 2 feet long, but it has a prostrate growth habit, so it is only about 6-inches tall. It can cling to dry walls, so it is a particularly good choice for rock gardens.
True geraniums have blue flowering cultivars, unlike the Perlargoniums that are sold as bedding plants and called geraniums. "Johnson's Blue" received the Award of Garden Merit from the Royal Horticultural Society when it was introduced. It grows about 18 inches tall, has a spread of about 15 inches, is drought tolerant and is hardy in USDA zones three to eight. It blooms late spring into summer. Geranium "Rozanne" is a brighter blue, blooms through midsummer and grows about 18 inches high. It received the Perennial Plant of the Year award in 2008.
Mazus reptans grows only 3 inches tall and forms a dense mat. It is often planted between stepping stones because it is tough enough to tolerate some foot traffic. The blue flowers appear in spring, and the plant is hardy in USDA zones five to eight.
Phlox subulata blooms in the spring in a variety of colors, including blue. Creeping Phlox is hardy in zones three to ten and has evergreen foliage in temperate regions. It only grows four inches high and likes sandy soil.
Veronica peduncularis "Georgia Blue" is hardy in USDA zones five to eight, prefers well drained soil and has strong blue flowers. It blooms in the summer and grows about 6 inches high. Veronica t. "Blue Reflection" is shorter, at about 3 inches and blooms in the spring.
In the Shade
Ajuga flowers in late spring, is tough enough to withstand some foot traffic and has cultivars with foliage in bronze, red, or yellow as well as green. It spreads rapidly and can be grown in full shade or sun. Most cultivars have blue flowers and are hardy in USDA zones three to nine.
Ceratostigma Plumbaginoides is hardy in USDA zones 6 to 9 and breaks dormancy late in the spring. It has brilliant blue flowers in late summer, and the foliage turns red in the fall. It grows about 10 inches high.
Phlox divaricata is a woodland plant that naturalizes readily, is hardy in USDA zones three to eight, prefers moist soil and grows about 12 inches tall. "Louisiana Blue" has intense dark blue flowers in late spring. "London Grove Blue" has light blue flowers in late spring and semi-evergreen foliage.
Mertensia virginica, the Virginia Bluebell, has bell-shaped blue flowers in the spring. This North American native naturalizes readily and is hardy in zones three to nine. It grows 12 to 24 inches in height and goes dormant in the summer.
Pulmonaria longifolia "Bertram Anderson" grows about 8 inches high and has semi-evergreen foliage with silver spots. It is hardy in USDA zones three to eight. The dark blue flowers bloom in spring.
Establishing and Maintaining
As with any plants, ground covers need a little care when they are getting started. The area should be free from weeds, and soil should be amended if necessary. For the first two or three seasons, the plants will need to be watered and weeded routinely. Once the ground cover is established, it is usually only necessary to weed in the spring. Many ground cover plants look better if they are cut back after flowering.