In his first article (October 2006), the author wrote about the hardy species of Impatiens that have begun to appear in the nursery trade. Here he continues with a discussion of the tender perennial species that are bursting onto the garden scene. For those who live in the warmer climates of the West Coast, or in a summer climate similar to the San Francisco Bay Area, the choices are huge. While not all of them would survive a freeze, they make first-rate annuals and perfect additions to a container garden.
In the Bay Area, a gardener can find one of the largest Impatiens in cultivation: Impatiens sodenii (syn. I. oliveri, I. uguenensis), an imposing giant commonly called poor man’s rhododendron. In the wilds of Kenya and Tanzania, this species can reach heights of nearly ten feet, with bright green, oblanceolate leaves, clothing the stem in whorls of up to ten. In cultivation, I have seen plants approaching this height, but most plants are plopped in a neglected spot in the garden and scarcely reach five feet. Yet, they often thrive in these sad locations, because, in the wild, they can be found in dry areas among boulders and on hillsides with little water. The form recognized by most gardeners was the one originally introduced as I. oliveri, with flowers of pale pinkish lavender and a thin spur tapering down below the bottom of the lower petals. The other, less common form was introduced as I. uguenensis, characterized by pure white flowers with a central eye of magenta, a nearly four-inch-long curling spur, and more spatulate leaves. For years, these were the only choices available; now, myriad new ones are appearing. One of the prettiest is I. sodenii ‘Madonna’, with pure white, rounded flowers up to four inches across; it resembles a large vanda orchid. Another interesting cultivar developed by Brad Cotton is I. sodenii ‘Flash’, which is much like I. uguenensis but with a pronounced magenta eye radiating from the flower’s center like a super nova. One hybrid between the two original forms is I. sodenii ‘Zanzibar’; it combines the best features of each parent in a pale, pinkish lavender flower with a deep magenta eye.
Another large species is Impatiens usambarensis, which can easily reach a more manageable four feet tall, with reddish stems and long lanceolate leaves. The large, hot pink flowers are similar to its close cousin, busy Lizzie (I. walleriana); the two species were once considered to be synonymous. Like its cousin, I. usambarensis is an easy plant to grow but has the added benefit of being somewhat hardier; it has survived in my Sacramento (USDA hardiness zone 9) garden for a couple of seasons beneath an evergreen tree. Native to the Usambara Mountains of eastern Africa, it will hybridize in the wild with I. walleriana, resulting in an orange-flowered, fuzzy-leafed balsam midway between its parents; about the same size as the bedding type, it has a more creeping habit with the hardiness of its taller parent. Seedlings of this hybrid may produce brilliant golden leaves, ruby red stems, and shocking orange flowers—a veritable riot of color.
The remarkable Impatiens niamniamensis has a wide distribution across the wilds of Africa, from Kenya to Cameroon. Its original collection was in southern Sudan, which was ruled by the Niam Niam, a people known for cannibalism. Lacking that unpleasant habit, I. niamniamensis does have a most scrumptious looking flower. Candy-corn flowers of orange, yellow, and green make ‘African Queen’ the most recognizable member of the several cultivars now available. Others are just as worthy, particularly ‘African King’ with dark green leaves and blood red flowers, and ‘Pink Princess’ with bright green leaves, pale pink petals, and a magenta pink spur. The red-spurred ‘Hare’s Hybrid’ and its sister ‘Renata’ are quite alike in appearance; ‘Hare’s Hybrid’ has reddish markings on the petals but narrower petals than those of ‘Renata’. The most outstanding cultivar yet is ‘Variegated African Queen’, which originated as a sport found by a grower in England; while the flowers are typical, the leaves are creamy yellow surrounding overlaid tones of green, making a beautiful display even without any flowers. All of these selections make a great show in the garden and, when happy, will flower from the base of the plant up to the tip, sometimes presenting a thick mass of blooms. This is a truly outstanding balsam.
As noted in my previous article, the flowers of many Impatiens species resemble the floral structure of orchids. Among the most intriguing are the oncidium types, such as the East African Impatiens cecilii and the similar I. stuhlmannii. I prefer I. cecilii, as it is much easier to grow and flower, tolerating more adverse conditions then I. stuhlmannii. Impatiens cecilii has a more upright and bushy habit than the other; though the two-inch flowers are smaller than I. stuhlmannii, they are just as eye catching, if not more subtly beautiful. The larger I. stuhlmannii can easily reach six feet in the garden, with large, pubescent leaves and broad, pink to magenta, oncidiumlike flowers.
In Asia, this flower form is adopted by Impatiens oncidiodes; though smaller than the previous two, it has wonderful lemon yellow flowers. Still rare in cultivation, it is proving to be a good garden plant for cool coastal areas. Impatiens falcifer may be the best of the group; an annual from the Himalayas, it sports bright yellow flowers with brick red speckling on the upper petal and, in some forms, on the large lower petals. This species remains rare in the US; it was introduced by a major seed company a few years ago (under the name I. oncidiodes) but, due to a crop failure, was not successful. It may, however, still exist in some gardens.
Impatiens auricoma is one of the newest balsams on the market. Native to the Comoro Islands off the coast of Madagascar, it is a little finicky about its growing conditions, preferring slightly warmer temperatures. In a greenhouse environment, it can reach four feet tall with long lanceolate leaves marked by a pinkish midrib. Originally introduced for its weird, bright yellow flowers, it soon found its way into hybridizing with the more common bedding impatiens (I. balsamina and I. walleriana). The first hybrids offered were the Seashells Series of four distinct colors, including the coveted yellow, which, unfortunately, faded to white in warmer areas. This series has now been replaced by the Fusion Series, offering the same color selections as the Seashells, but the new yellow version is much larger with two distinctive red dots on the lower petals.
Impatiens auricoma seems to be part of a large group of Madagascar species that will readily hybridize with each other. A few years back, a seed strain of I. auricoma hybrids was introduced under the name “African Orchids.” This greatly expanded the color pallet of I. auricoma to lavender, orange, and amber. Unfortunately, the plants become weaker with age and have to be regularly renewed by cuttings.
For lovers of red flowers, up steps I. bicau-data ‘Madagascar Red’, a five-foot-tall balsam with a thick trunk approaching eight inches around at the base; alas, it is a seasonal bloomer, producing flowers mostly in the fall. I crossed I. bicaudata with I. ‘Kenya’, a lavender “African Orchid.” What appeared was I. ‘Big Red’, an exotic, red-flowered giant like I. bicaudata with the free-flowering habit of I. ‘Kenya’. When ‘Big Red’ starts to bloom, it never stops, each stem producing great clusters of flowers at its peak. Even during the heat of summer (its offseason), it will have several flowers open and will produce more as the weather cools.
Not all of the new balsams are big plants; many are small but pack a huge punch. The widespread African species, Impatiens hochstetterii, has small, pinkish, butterfly-like flowers but the plant is anything but delicate. A strong grower, it will reach about three feet across and a foot tall. When happy, I. hochstetterii will easily set seed and can take advantage of any available space, sometimes coming up in cracks in pavement (a potential red flag for those concerned about invasive exotics). A fellow African, I. zombensis shares this self-seeding tendency but has a much more sultry appearance. Its leaves are a beautiful deep forest green on dark red stems that creep along the ground producing small, magenta, people-shaped flowers.
My hybrid of Impatiens digitata and I. meruensis is variable in flower shape. The parents were growing near each other when this seedling appeared. Some have cupshaped flowers like those of I. digitata, while others produce flat pink flowers like I. meruensis, but there are all shapes and colors in between. In the San Francisco Botanical Gardens at Strybing Arboretum, it has made its presence known, almost completely replacing the two parents. Beyond the Bay Area, it has a tougher time surviving and definitely does not relish the hot summers of the interior valleys.
Other creeping Balsams are perfect choices for damp shady spots. Impatiens burtonii is one of a complex of species that would make excellent garden plants but are not yet in cultivation. It is another African species with ground-hugging stems that root as they spread; just above the foliage rise the strangely beautiful pink flowers. Closely related to I. niamniamensis is Mount Kilimanjaro balsam (I. kilimanjari), another species that dislikes dry heat and will quickly melt away under such conditions. With cool summers and moist soils, it will thrive and produce cherry red, yellow-spotted flowers among the shiny green leaves. If you grow its Kilimanjaro relative, I. pseudoviola, you may get natural hybrids in an array of forms. Impatiens pseudoviola is fairly new to the US, but it can be found easily in England where it is used as a bedding annual like I. walleriana.
Apparently tolerant of cold winters are two distinctly different Chinese species: Impatiens mengtszeana and I. rhombifola. The first is a robust balsam, best used as a ground cover; the alien-looking, apricot yellow flowers begin to appear in the fall. It has sailed through 25° F in flower in North Carolina; in California, it became mush in cold rainy weather but bounced back in spring, bigger then ever, from its roots. The much smaller, yellow-flowered I. rhombifola has an interesting past: in its travels to the West Coast, it found its way from China first to Japan, then to Paris where it grew along the River Seine before finally arriving in California. In its dormant stage, cute black-spotted leaves, barely a quarter-inch wide, appear in tiny rosettes. When the weather warms, the plants lunge into growth, forming a mass of stems that lie flat and take root, making way for the next year’s rosettes.
Described only in the last couple of years is Impatiens nyungwensis from Africa, and it offers a story of hope. After its description, the habitat where it was found was destroyed to clear the forest for agriculture; it now appears that I. nyungwensis may be extinct in the wild. Only the original collected material was saved, but the good news is that plants were grown from the seeds, and those plants set seed easily, though it is less prolific than some species. Out of flower, I. nyungwensis resembles species such as I. digitata, but the flowers are completely different; peeking out from beneath the leaves, the bright orange red flowers have a curling spur and a bright green upper petal—in striking contrast to the rest of the flower.
Most Impatiens are easy to grow, preferring cool moist areas with a rich loamy soil. Pest problems are minimal for adult plants, but slugs and snails may munch on seedlings. Aphids are the major concern, and, in drier climates, mites. These usually betray themselves by a distortion of the leaves and flowers. Keep an eye out for these pests and control them when they appear to be causing damage.
Though Impatiens are not drought tolerant, they do need to be grown more. With rain forests disappearing at a phenomenal rate, these little jewels might also vanish if we only grew native or water conserving plants in our gardens. The only hope for many wild plants such as Impatiens is conservation through cultivation; without us, they may be lost from this Earth forever.
An Impatiens Resource Guide
For a list of nursery sources for the Impatiens described in this article, see the author’s first installment in the October 2006 issue of Pacific Horticulture.