Wildly Successful: Impatiens sodenii

Impatiens sodenii. Photograph by David Goldberg

Impatiens sodenii. Photograph by David Goldberg

For some years after its introduction into Northern California gardens early in the last century, Impatiens sodenii spread mainly by cuttings shared among gardeners, rather than from plants purchased at nurseries. It earned the common name “poor man’s rhododendron” by quickly producing large flowering shrubs from these cuttings. Plants bloom much longer than rhododendrons, opening new flowers throughout most of the year. The stems bear whorls of six to ten rhododendron-shaped leaves, each whorl producing a succession of two to two-and-a-half inch, pale to mid-pink blossoms that fade to nearly white as they age. Behind each flower is an long, elegant petal spur.

This is a plant of the East African tropical highlands, found in central Kenya and north central Tanzania at elevations from 3,000 to 8,100 feet, where it grows at forest margins and on rocky slopes. I like to picture it growing, as reported in one book on Kenyan wildflowers, “near waterfalls and streams and in misty situations.” However, its somewhat succulent, moisture-storing, stems enable it to grow in drier, more exposed conditions, even in cliff crevices, where plants are squat, with smaller leaves and flowers. It has also been transplanted into gardens in many parts of Kenya. Rainfall in the region varies from twenty to forty inches a year, with a long spring rainy season and a shorter one in fall. Temperatures at the elevations where this impatiens grows typically range from lows of 50-60° F in the cooler summers to late winter highs in the 80s.

Impatiens sodenii was first cultivated in England’s Kew Gardens in 1902. The first record of it in the Bay Area was in a 1913 estate garden on the Peninsula. By 1931, it was being grown in Golden Gate Park, and, by the 1960s, it had become a rather common Bay Area plant. It is handsome in a tall mixed shrub border, and can be kept shorter to grow in a low border or trimmed to fit a narrow bed. Before the fuchsia mite destroyed most of the region’s hybrid fuchsias, Impatiens sodenii and fuchsias were a common garden combination.

This species of Impatiens is adaptable to various soil types and can survive with little or no irrigation, though it will look best in moderately fertile soil with moderate summer water. Good drainage is essential. If the soil becomes too dry, lower leaves will turn reddish, then yellow, and then fall off. Areas with coastal influence are ideal, replicating the moderate temperatures of its homeland. Frost-damaged plants can re-grow if the root crown survives, but plants do not last long if that happens every year. It is best in USDA hardiness zones 10 and 11, where the temperatures rarely drop to freezing; Sunset lists it for zones 15-17 and 21-24.

Prune lightly year-round to shape and groom plants, removing discolored leaves and shortening overly long branches, but don’t prune too heavily at any one time, or you will reduce flowering. Cut plants back hard in March to remove any frost damage and keep them compact. If canes are crowded, thin them at this time, cutting to the ground those that are most spindly or have few leaves. After five years or so, you may want to dig and divide the crowded clump of canes into two or more new plants.

Like other impatiens, this species has seedpods that burst open at a touch when seeds are ripe. To collect the seeds, identify a ripe pod and grasp it quickly so the seeds will pop into your hand. Ripe pods are bulging, but still green and quite succulent. While seed is fun to collect and germinates easily, stem cuttings are a much faster way to propagate the plant. These will root at any time of year, but spring and summer are best.

Impatiens sodenii will re-seed in California, but usually not abundantly; unwanted seedlings are easy to pull out. As there is only one flower color currently available, seedlings will bloom true. If other colors become common in gardens, we will only be able to ensure the flower color of new plants that have been grown from cuttings.

We should be aware that this plant has escaped cultivation in New Zealand and in Costa Rica, though there appears to be no evidence that it has done so to any significant extent in Northern California. Once dug out of a bed, the plants do not re-grow from pieces of root left behind.

Pale pink flowers of Impatiens sodenii with purple flowers of Rhododendron ponticum. Author's photograph

Pale pink flowers of Impatiens sodenii with purple flowers of Rhododendron ponticum. Author’s photograph

Varieties and Similar Species

You may find this plant in nurseries under various former names that include Impatiens oliveri, I. uguenensis, and I. magnifica. A form with red-marked white flowers has been marketed locally as I. uguense in recent years, and pure white-flowered forms have long been in cultivation in Britain. Lavender and purple flowers have been reported on wild plants.

European plant explorers came upon this species in the East African highlands, several times between the early 1890s and 1935. They all knew that it was in the genus Impatiens, but several of them gave it different species names. The international botanical congress decided that the first, and therefore valid, name was I. sodenii, a name given this plant in 1894. We know that the genus name Impatiens (im-pay’-shens) is simply the Latin word for impatient, but the authors did not reveal the reason they chose the species name sodenii (so-den’-ee-eye). Plant collectors often named plants after other botanists, friends, relatives, or even politicians. We can tell from the Latinized ending of this species name that the person for whom this plant was named was male, but all else is lost to history.

Adapted from Wildly Successful Plants for Northern California Gardens, by Pam Peirce with photographs by David Goldberg, to be published by Sasquatch Books in January 2004.