Lewisias are dainty alpine plants—some deciduous, some evergreen—first discovered by Lewis and Clark on their expedition in 1804. Some species are still being discovered in mountainous areas of the western U.S. today. Lewisias have thick roots—which served as food for Native Americans, as well as for Lewis and Clark—and rosettes of leaves which are crowned in spring with blossoms of pink, red, white, purple, yellow, or orange, depending on the species. Lewisias have become a popular if somewhat difficult rock garden subject. However, when their needs for water and drainage, light, and space are met, they have been grown successfully in New England, Great Britain, and in pot gardens in many climates.
Water and Drainage
When lewisias are growing, they need an adequate amount of water, but never too much at one time. Water and drainage necessarily go hand-in-hand; the plants must be sited in a perfectly drained area so the roots and crown never stand in water. A deep, loose, gritty soil-gravel mixture of slightly acid to neutral pH is useful for this. After spring growth and flowering, water requirements for the rest of the season are minimal; dry, cool summers suit their alpine heritage.
Light
Deciduous lewisias do not like being shaded by larger plants (even as they do not like being dripped on): a site in full sun is preferred. Evergreen lewisias do well in light shade.
Space
Lewisias also do not compete well for growing room; they need to have ample space set aside, often thriving in crevices and niches.
Problems with Growing Lewisias
Major diseases in lewisias include damping off of seedlings and fungal disease.
Damping Off
Damping off, the sudden demise of healthy seedlings due to stem weakness or root rot, caused by a fungus, can best be controlled by ensuring adequate ventilation of seedlings and sterile sowing conditions.
Fungal Diseases
Lewisias seem unfortunately prone to fungal infections. Species of the fungal Botrytis family may be responsible for the rapid deterioration of specimen plants. Dry plant surfaces along with good drainage and air circulation will help minimize risk of this fungus. If the integrity of the leaf surface is broken—as by ice—the leaf may be exposed to infection. In addition, the roots are attractive to some fly larvae which feed on the tissue, in turn leaving the root tissue vulnerable.
Garden Pests
The usual gamut of garden pests—including slugs, aphids, mealybugs and sowbugs—can be troublesome as well.
This said, lewisias remain very hardy additions to rock gardens if their needs are met. In the wild, individuals of some species have survived more than 40 years.
Sources
Davidson, B.LeRoy. 2000. Lewisias. Portland: Timber Press.
