Arboretums are places of experimentation, where experts work to discover what plants can grow in our climate and how best to grow them. The autumn months are an especially busy time at Southern California's botanical gardens. Says Francis Ching, director of the Los Angeles State and County Arboretum system: "We wish we could plant everything in the fall, but we have to spread the work out. So in the fall, we concentrate on those things that must be planted now--spring's flowers and bulbs." Fall is the best time to plant just about everything in the California garden--spring flowers and winter vegetables, bulbs, perennials, ground covers, shrubs and trees. Last spring, we photographed some of what botanical gardens had planted the previous fall. Discussions with four of the gardens' plantsmen led us to some fascinating combinations of plants and some surprising cultural tips.
VOLUNTEERS DO MOST of the fall planting in their own corner of this very large and under-funded garden, but not everything is planted at the proper time because many of the plants are donated by nurseries after their fall sales. In fact, some spring flowers aren't set out until early February. But they still manage to bloom in time for spring.
Full of wonderful and often-unexpected mixes of flowers, this former dump site looks like a cottage garden in a storybook. "Because this garden is planted entirely by our volunteers, they can do whatever they want," says Norma Cantafio, who directs the volunteers' South Coast Botanic Garden Foundation.
Surprises occasionally come from flowers that return each year from seed. Red flax and calendulas are two varieties that make a delightful mix, reappearing on their own each winter, if the volunteers simply water and weed.
A big bed of Tecolote ranunculus planted from tubers in October is also full of linaria, which looks like baby snapdragons. (The garden is so wild that the occasional weed--in this case, the sow thistle--sneaks in.) The same effect could be achieved by purposely sowing seeds of these easy-to-germinate annuals--especially the red flax ( Linum ) and the linaria--among other plants.
DESPITE ACRES of camellias, roses, perennials and fall-planted annuals, tulips are superintendent George Lewis' favorite spring flower. Not only does he grow them on a scale unheard of in California, but he also grows them perfectly--not an easy feat here.
Lewis and his staff buy bulbs as early as possible and immediately refrigerate them for a minimum of six weeks. Loamy clay soil is amended with organic matter, plus an amazing addition: A four-inch layer of washed builder's sand is mixed in to improve drainage. "Tulips hate wet feet," says Lewis, who landscaped rooftop gardens in New York City before joining the Los Angeles arboretum system 30 years ago.
Bulbs are planted 8 to 12 inches deep, much deeper than the usually recommended 6 inches. (Planting occurs at the end of December, in time for an array of blooms for the Spring Garden Show that begins on April 1). A handful of bone meal is dropped into each hole, and bulbs are set on top of it. They are not watered but survive on rainfall and moisture already in the soil (beds are thoroughly watered a few days before planting) until foliage breaks through the ground. Withholding water prevents rotting and encourages what Lewis proudly terms a "massive" root system.
After leaves appear, plants are watered frequently--every other day by March. When new growth reaches 3 inches, high-nitrogen liquid fertilizer is applied every two weeks. As flowers wither, bulbs are pulled out of the ground and tossed on the compost heap. Tulip bulbs grown here are not successfully recycled, as they are in the East Coast. "Only three out of 10 would return next year," Lewis estimates.
BECAUSE THIS GARDEN is devoted to native California plants, horticulturist Carol Bornstein keeps a close eye on weather forecasts. She plants just before fall's first good rain, usually in November. In October, she and her staff decide what to plant and ready seed. Then they wait.
Wildflowers are annual plants and must be sown from seed every fall, but Bornstein, who has a master's degree in horticulture, reports that she no longer tries to plant huge meadows of them. Instead, she says, her staff is "dribbling in wildflower seed in smaller swaths" because weeds can quickly smother wildflowers and smaller areas make weeding easier. Permanent clumps of native bunch grasses and perennials break up these meadow areas so that they don't look completely bare in summer. For example, the buttercup-yellow meadow foam, Limnanthes douglasii , disappears for the summer. California poppies and blue-eyed grass, a blue-flowered relative of the iris, hang on.