There are many shades of white and there are flowers in almost all of them. Think about cream, antique white, pearl, chalk, and snow white. Each varies from the others and has qualities all of its own. Some flowers start out one shade of white and change as they open and then fade away. Some plants have silvery white or variegated white foliage to add whiteness to the garden. White goes with every other color and is a good transitional color. It also affects the appearance of the colors around it, softening pastels, and making reds and blue more prominent. White flowers in the rock garden can be useful or beautiful for their own sake.
Here are five summer blooming perennials that produce white flowers.
Sandwort (Arenaria montana)
Large white flowers are produced above low mounds of dark green foliage in early summer. The evergreen plants have long trailing stems and grow quickly from a central crown but do not take root as they grow. They look spectacular cascading from a wall.
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Size: 8” x 24”
Light: Full sun
Soil: Average, well-drained
Hardiness: Zones 5-8
Creeping Baby’s Breath (Gypsophila repens ‘Alba’)
Gray-green foliage forms mats with creeping stems and provides the background for small white flowers. Flowers of the species may also be pink so look for ‘Alba’ if white is the color of choice. Plants are excellent wall plants.
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Size:4-8”H x 12” W
Light: Full sun
Soil:Average, well-drained; prefers but does not require lime in the soil
Hardiness:Zones 3-8
Irish Moss (Sagina subulata)
Irish moss is not a moss and also goes by the common name pearlwort. But the misnomer, irish moss, gives an idea of the handsome attributes of this unusual plant. This semi-evergreen plant is low growing, very fine textured and is sprinkled with tiny white flowers. Except for the flowers, it looks a lot like moss and is attractive used between stones in a path. It can be invasive, however, and overwhelm a small rock garden.
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Size:2” H x 10”
Light:Full sun to partial shade
Soil: Average, moist; does not tolerate drought or wet feet
Hardiness:Zones 4-8
Alps Campion (Silene alpestris)
A low, trailing evergreen tuft or mound of deep green glossy leaves bears open sprays of white flowers on short stems. The flowers resemble those of Dianthus and are produced over a long time.
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Size:4-6” H x8-12” W
Light: Partial shade or full sun
Soil: Average, gritty, well-drained; does not tolerate extreme dryness
Hardiness:Zones 4-9
Alpine Aster (Aster alpinus)
Alpine aster has the typical daisy-like flower with a yellow center held above low tufts of grey-green leaves and are useful in alpine meadows as well as the rock garden. Flowers may also be pink or blue with yellow centers. Unfortunately, the plants are short-lived, surviving about 3-4 years.
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Size:6-9” H x 12” W
Light: Full sun
Soil: Average, well-drained
Hardiness: Zones 4-7
Four of these perennials are low growing mat forming plants. The fifth, alpine aster, stands out with more distinct flowers with yellow centers that make the flowers seem all the more vibrant. Most rock garden plants can tolerate some dryness but alps campion and Irish moss can not. In addition, these two plants can take some shade, especially in warmer parts of their range.
