GARDENING : MADAGASCAR'S RIVAL TO IMPATIENS.

Byline: Joshua Siskin

Impatiens - that multicolored staple of the shade garden - finally has some competition.

Actually, this competitor has been around for some time, but has not been promoted as a bedding plant for the shade. Wherever impatiens grow well, you can plant it too. I'm talking about Kalanchoe blossfeldiana, that popular succulent, a favorite of the florist trade, with flowers in red, pink, salmon, orange or yellow.

This will come as no surprise to the geobotanists among you. Impatiens is native to Mozambique, on the southeastern edge of Africa. Kalanchoe is indigenous to the island of Madagascar in the Indian Ocean, off the coast of Mozambique. The cheek-by-jowl habitats of these plants means that they may well have similar cultural requirements.

There are three benefits to growing kalanchoe (pronounced ka-lan-koh-ee), as opposed to impatiens, in the shade garden. First, kalanchoe is a long-lived perennial, while impatiens is unlikely to survive for more than a year in most gardens. Second, the succulent, thick-leafed kalanchoe does not require as much water as the more fragile impatiens. Third, kalanchoe is easily propagated by stem or leaf cuttings at any time throughout the year. Kalanchoe also propagates itself, without human assistance, in two ways: It produces adventitious roots, through ground layering, wherever its stems bend and touch the ground; if its dried-up flowers are not snipped, but left on the plant and allowed to go to seed, a crop of new kalanchoe seedlings will germinate around the existing plants after a rainy winter.

Kalanchoe is a short-day plant, which means that it initiates flower buds between Oct. 15 and Feb. 15. Since it takes three to four months for kalanchoe flowers to open from the moment their buds begin to grow, they should provide color over a six-month period - between the middle of January and the middle of June - under normal garden conditions.

You can find kalanchoe blooming in a florist's shop at any time of the year for the same reason you can find chrysanthemum - another short-day plant - blooming there at any given moment. Between Feb. 15 and Oct. 15, plant growers cover short-day plants with black cloth for 15 consecutive hours of every 24, mimicking short-day conditions. In this way, they can keep their short-day plants blooming throughout the year.

Through David Bernstein of California Nursery Specialties, I learned about some arborescent kalanchoes that make fine, low-maintenance specimen plants. Kalanchoe beharensis has furry, triangular gray and brown leaves and reaches 20 feet in height. Kalanchoe beharensis ``Fang'' is a cultivar with somewhat mysterious and altogether frightful fangs growing out of the bottom of its leaves.

Since Kalanchoe blossfeldiana blooms in winter and spring, that still leaves six months of the year to color up the shade garden. Bernstein has a number of recommendations for achieving year-round color with succulents. Not on account of their flowers, but because of their variously colored leaves.

Senecio mandraliscae and Senecio serpens have succulent blue fingers for leaves and grow well in low-light conditions. Aeonium (``Sunburst''), whose rosetted leaves bear stripes of green, pink and yellow cream, grows under similar conditions. Echeveria (``Afterglow'') has violet blue leaves, and Echeveria gibbiflora hybrids have leaves in colors ranging from burgundy to lavender. Aeonium arboreum (``Zwartzkopf'') has very dark red to blackish leaves.

These are available at Bernstein's nursery, located at 19420 Saticoy St., Reseda; [phone]. The nursery is open to the public from 11 a.m. to 6 p.m. Saturday and Sunday only.

Tip of the week: If you become a plant enthusiast in Los Angeles, you will eventually reach the conclusion that reliance on sprinklers renders the development and maintenance of interesting gardens impossible. Yes, you can grow agapanthus, begonias, calla lilies, rhaphiolepis - and certainly a fine lawn - with the help of sprinklers. But, to grow an interesting garden, with plants of many shapes and sizes, from different habitats and with varying water requirements, sprinklers will be more of a hindrance than a help. Sprinklers do not water evenly, their spray deflected by your plants as they grow to maturity. Some plants will receive too much water, and others not enough. Many Mediterranean climate and California native plants die if they get a drop too much to drink in hot weather. And then there is the false sense of security, created by sprinklers, that everything is being properly watered. If I could give but one bit of advice to new gardeners in this town, it would simply be: Forget about sprinklers and get comfortable using a hose.