Rainbow Lewisia Plant Profile

Perennial Honors Special Event in U.S. History

Lewisia cotyledon Rainbow Mix plants in bloom.
David Beaulieu

Rainbow Lewisia is a cultivar of a succulent-like plant that is not among the easiest plants to grow in the yard. But this perennial does offer attractive flowers and foliage, and gardeners in the eastern United States may well wish to grow it as a novelty. It is in the purslane family, as is the weed, common purslane (Portulaca olearacea), and the annual popular as a bedding plant in dry areas, moss rose (Portulaca grandiflora). Learn how to overcome the challenge in growing it and what the plant has to do with a famous event in U.S. history.

Botanical Name Lewisia cotyledon 'Rainbow'
Common Name Rainbow bitterroot, Rainbow Lewisia, Siskiyou Lewisia, cliff maids
Plant Type Evergreen perennial
Mature Size 8 inches tall (when in bloom), with a greater spread
Sun Exposure Partial sun to full sun
Soil Type Average fertility, excellent drainage
Soil pH Acidic to neutral
Bloom Time April, May, and June
Flower Color Salmon, white, orange, pink, rose, or yellow
Hardiness Zones 5 to 8
Native Area Several western states of the U.S., and British Columbia in Canada

How to Grow Rainbow Lewisia

Give Rainbow bitterroot a soil that drains extremely sharply (sandy or pebbly soils work best). Having ground that drains well is very important, because crown rot is a pervasive problem with Lewisia, especially in cold weather. Its susceptibility to crown rot also means it is critical to ensure that the crown sits above ground level when you install the plant in the ground. Its habitat in the wild is scree, so it can survive in poor soils and makes a good rock garden plant.

You can further provide the drainage this perennial so craves by applying a gravel mulch around it. Some gardeners who grow the plant in a container set the pot on its side during the winter to avoid any buildup of excessive moisture around the crown. In terms of pest-control measures to take, you may have to kill slugs if you notice holes being chewed in the leaves.

After blooming, deadhead it to foster further flowering. You can also gain more plants after flowering is over as you would with hens and chicks (Sempervivum tectorum), separating the babies from the mother plant and transplanting them. 

Light

Locate this perennial in full sun in the North (it can profit from some shade in the South).

Soil

Rainbow bitterroot needs an extremely well-drained soil.

Water

Although Rainbow bitterroot plants are considered drought-tolerant perennials, it is still a good idea to provide them with water during hot weather (especially while they are flowering) if you are growing them in full sun. However, it is essential that their roots not be sitting in water during the winter (thus the need for sharp drainage).

Fertilizer

Rainbow bitterroot has average fertility needs (for best flowering).

What Rainbow Lewisia Looks Like

The waxy, sword-shaped leaves grow in rosettes and are leathery to the touch. While this foliage is an asset, the plant is primarily grown for its pastel flowers. By buying the Rainbow Mix, you can have some combination of salmon, white, orange, pink, rose, and yellow flowers. Often, if you look closely at the petals, you will see that they have white stripes. Some Lewisia plants have flowers that are altogether white.

The flowers bloom in clusters atop long, fleshy stalks (from ground level to the flower tops, the plants stand about 8 inches tall). The plants can spread by having a "mother plant" send out babies (what horticulturists term "offsets") directly from itself.

Varieties of Lewisia

Its German marketers gave it the name, 'Regenbogen' (which means "rainbow"), and you may come across that cultivar name as well in your research. It is also sometimes sold at garden centers as 'Rainbow Mix' because what you're buying is two or three individual plants (growing close together in one pot), each of which can flower in a different color. Other cultivars include:

  • 'Sunset Strain' (similar to Rainbow)
  • 'Elise' (or 'Elise Mix;' also similar to Rainbow, except that it blooms more easily from seed in its first year)
  • 'Ruby Red' (a cultivar of just one color: deep-pink)

In addition to L. cotyledon, some other kinds of Lewisia are:

  • L. rediviva
  • L. longipetala
  • L. columbiana

L. rediviva is the state flower of Montana. The indigenous peoples had both culinary and medicinal uses for it. L. longipetala ("long-petaled") was hybridized with L. cotyledon, a union that resulted in the cultivar, 'Little Plum.'

Origins of the Names, Place in History

The genus name of Lewisia comes from American explorer, Meriwether Lewis. Lewis and Clark encountered Lewisia rediviva on the famous expedition (1803 to 1806) they undertook at the behest of President Thomas Jefferson and brought back specimens. Frederick Pursh, a botanist, is responsible for the name. Pursh also established the genus, Clarkia in honor of the other famous explorer in the duo, William Clark.

Jefferson had a great interest in botany. A genus is named for him, as well: Jeffersonia. Think of LewisiaClarkia, and Jeffersonia as the all-American plant trio.

The reason why a common name for Lewisia is bitterroot is that, although the root of L. rediviva is edible, it is very bitter until it has been cooked thoroughly. The plant gave its name to Montana's Bitterroot Mountains, Bitterroot River, and Bitterroot Valley.

Uses in Landscaping for Rainbow Lewisia

Try growing your plant in a portable planter, which allows you to use it in a number of ways. But whether you grow it in the ground or in a container, here are some of the uses for Lewisia cotyledon 'Rainbow':