Androsace are absolutely beautiful Alpine plants. They're related to primroses, and have a similar, cheerful bloom shape, but the flowers are generally much smaller, with several tiny white flowers growing on each flower stalk. If you live in a cold region and have a rock garden or areas with lean, poor soil, this is a plant you might want to consider.
How to Grow Androsace
Androsace are often high alpine plants, so cold temperatures, rocky or gritty soil, and dry conditions are where they thrive. They don't suffer from drought, they don't need additional fertilizer, and they're not likely to be picky about soil (unless you have wet, heavy soil, which is the opposite of what they need to grow well).
If you have a rock wall, androsace grows well in small fissures between stones, firmly packed with pure sandy peat, or very sandy or gritty loam. Once it's established, androsace isn't likely to suffer from drought, even during the driest periods.
And if you don't have a rock wall, androsace also grows well at the edges of garden beds, in troughs, or in other shallow containers filled with a coarse planting medium, similar to what you'd use for succulents and cacti.
Most androsace varieties are hardy in Zones 3 through 8.
Most androsace thrives in full sun, and if you have areas with southern or western exposure, that's even better.
Pests and Diseases
Aphids and slugs can sometimes be a problem during the summer. Check your plants regularly for any signs of these pests.
Aphids can be washed off with a blast of water from the hose, and slugs can be picked or trapped and then destroyed.
Preparing Androsace for Winter
Towards autumn, it's a good idea to give them a bit of water before the ground freezes, unless you live in an area that gets plenty of rain during the fall.
It's also a good idea to mulch the area with pebbles or small stones, since this will not only help the soil retain moisture and reduce weeds in the spring, it will also help you identify where you planted these tiny plants to begin with. As a bonus, many androsace spreads via its stems, with new roots forming along them as they creep along the surface of the soil. If you provide a substrate of coarse pebbles, it will be that much easier for you to remove these new plants, roots and all.
Varieties of Androsace
There are over 40 known species of androsace. About twenty kinds are found in the Alps, some extending eastward by way of Austria, or southward to the Pyrenees. A large group is also native to the Himalayas. Not all are cultivated for home gardens, though there are several varieties available in plant catalogs.
This is one of the mossy kinds of androsace, forming small rosettes of deeply-toothed oval leaves and dense heads of pale pink flowers from April to July.
A gem for the rock garden, A. alpina is not easily grown. Its tiny tongue-shaped leaves are in crowded rosettes, forming cushions of two or three inches high, covered in June with flowers, one from each rosette, rosy-purple with a yellow center. It needs peat soil, moisture at the root, and a rather shady spot.
A. brigantiaca thrives only in sandy or granite soils and on slopes shaded from strong sun. It has deep green leaves and pure white flowers.
Carnea is one of the most desirable varieties of androsace for gardeners, early to flower, easily grown in light soils without lime. It does not form rosettes, but little spreading shoots covered with narrow-pointed leaves of gray-green, and heads of rosy or pink flowers with a yellow eye. Water freely in dry weather, and shelter from the sun in summer.
Androsace Carnea var. Eximia
This is a close relative of A. carnea, but hardier and more robust, and with larger flowers. It grows quickly into tufts three inches high, and if given dressings of light, gritty soil, the prostrate shoots send roots from the underside.
This variety produces numerous flowers and has strong growth in sandy soils. Rosettes of tiny, downy leaves in crowded masses, and rich rosy flowers hardly rising above the leaves in June and July, after other kinds have done flowering. It thrives best in crevices of sandstone or granite rock, facing southwest.
A. ciliata is a somewhat rare plant from the Pyrenees, which grows in small, dense columns of deep green leaves fringed along the edges, and crowned in April and May by large stemless, bright rose-colored flowers.
Though classed as a species, this little plant is very similar to Androsace ciliata, and comes from the same region. It forms mossy tufts of rounded cone-like columns less than an inch high, covered thickly with hairs, with white flowers nestling in the center during April and May.
Androsace foliosa is native to the Himalayas. The plants creep along the ground, and the leaves are gray with pale hairs, turning reddish-purple in the autumn. The rosy flowers bloom on long stems from June to September, and are large and in clusters sometimes of fifty flowers, lasting for a long time.
This is a charming plant that grows in a low, moss-like habit, forming little rounded, grayish-green cushions of foliage. Tiny, white flowers with a yellow eye bloom in early summer, covering the tufts in masses of cheerful blooms. A. helvetica thrives in gritty soil and partial shade.
Androsace hookeriana has rosettes of oval, shining green leaves, and blooms in spring, producing clusters of deep pink flowers.
Androsace lactea forms rosettes of shining green leaves, and in spring it produces large white flowers with a yellow center. It grows best in full sun or partial shade.
Androsace laggeri forms clusters of narrow-pointed leaves, and flowers of bright pink paling towards the center, gathered into showy little heads of six or eight. It's very hardy, it is one of the earliest alpine flowers to open, starring the green tufts like a miniature Thrift. It grows best in sandy soil in partial shade.
Androsace lanuginosa has trailing silvery shoots, leaves covered with silky hairs, and flower clusters of soft rose color. It does best in warm places near the sea, planted in sunny corners of the rock garden. Where the soil is free and open, it thrives as a border plant. It has a long season of flower, even lasting into October, growing best in south and west aspects, in sandy loam.
Androsace obtusifolia is robust and easy to grow, with large rosettes of spoon-shaped leaves fringed by fine hairs, and short downy stems carrying from one to six white or rosy flowers with a yellow eye. It is nearly six inches high, and blooms in mid-summer.
Androsace pubescens is a mossy variety with leaves that turn red-brown in autumn. It may be known by a small swelling on the very short flower-stem, just below the flower. These are white, rather large, with a faint yellow eye, and come singly just above the little cushion of hoary leaves covered with star-like hairs.
Androsace pyrenaica is another mossy variety, with tiny gray rosettes in dense tufts, one flower from every tuft. Its flowers are similar to Androsace helvetica, though this is much less commonly grown than A. helvetica, since it's more difficult to grow.
Androsace sarmentosa has leaves that form dense rosettes. The foliage is fuzzy and silvery, and it forms slender runners which spread and root in all directions. This kind spreads quickly in ideal conditions.
Androsace sempervivoides is a rare plant, but if you can find seeds or transplants, it's worth growing. It's pretty, easy to grow, and spreads by runners, so it acts as an attractive groundcover. It blooms in late spring and early summer, forming clusters of pink or purplish flowers.
Androsace villosa has white or pale pink flowers and silvery leaves with long, white hairs, giving the plant an overall fuzzy, soft appearance.
Add Beauty to Your Rock Garden
Androsace might be just the plant you're looking for to add beauty and interest to your rock garden. Be sure to plant it in plenty of sun, and in soil that has a coarse texture, and you can enjoy this alpine plant for years to come.