Gardening : Colorful Blossoms Are Unfazed by Drought : Conservation: Water-saving vines, shrubs, trees thrive in Southland even in a garden on a water diet.
The ‘90s are the decade of the environment, but let’s say you were ahead of the times. A few years ago you realized Southern California’s water shortage could only get worse, so you revamped your garden with water-saving plants native to California and other Mediterranean climates.
Now each spring your garden is ablaze with flowering shrubs--rockroses, acacias, mountain lilacs, sages, grevilleas and lavenders--over a carpet of native wildflowers and South African bulbs. This colorful blend of plants perfectly suited to our climate is all you envisioned--it looks great and saves water.
Still you have twinges of regret this time of year when you drive down the street and see trees densely covered with gobs of trumpet-shaped sulfur-yellow flowers that practically shout out their tropical origins.
And in summer when your neighbor’s Barbara Karst bougainvillea is a mass of red blooms, and all you have are the tiny white flowers of your California holly bush, you could almost weep with envy. But if the garden is on a water diet those tropical flowering trees and vines must be as far off limits as pizza and hot-fudge sundaes, right?
Wrong! Those spectacular yellow blossoms belong to golden trumpet trees ( Tabebuia chrysotricha ), and, according to the “Sunset Western Garden Book,” they can withstand much drought once established. Bougainvilleas, too, are extremely tough, and old plants can be seen surviving on rainfall alone in neglected gardens. Despite their reputation as jungle-dwelling water guzzlers, many beautiful tropical flowering trees, vines and shrubs are native to areas with dry seasons as long as our own.
This spring planting season gardeners can add a new dimension to their water-conserving landscapes with a few well-chosen tropicals. One small flowering tree to look for is giant thevetia ( Thevetia thevetioides ). Introduced to California from Mexico decades ago by the famed Evans & Reeves nursery, this shrub or tree to 12 feet tall bears large yellow, funnel-shaped flowers in warm weather and is hardy to 27 degrees.
Flowering vines are scarce in the Mediterranean floras but they are the glory of the dry tropics. Among the many tropical American vines that have been grown for generations in California are cup-of-gold, coral vine, cat’s claw and bougainvillea.
Bougainvillea is both beloved for its lavish displays and reviled for its enormous bulk, which can threaten to crush a wall it is trained on. Fortunately, in most nurseries you will find new smaller-growing varieties, including a dwarf called rosenka that is gaining favor locally as a mounding ground cover. Its bracts (the colorful parts that resemble petals) start out orange and age to a beautiful salmon-pink, a welcome change from the usual purplish-red bougainvilleas.
Queen’s wreath ( Petrea volubilis ) has been hailed as one of the world’s most ornamental vines but is seldom seen in California, perhaps because it is rather tender to frost. Nevertheless, this large climber native to Central America performs superbly in the mildest areas of Los Angeles, producing its long clusters of purple, starlike flowers for months at a time. It needs ample watering to bloom continuously, but an established queen’s wreath can also survive a drought. Queen’s wreath and giant thevetia may be hard to find in nurseries, but your retail nursery can order them from Monrovia wholesale nursery.
Many plants from the dry tropics of Mexico are available at Desert to Jungle Nursery (3211 W. Beverly Blvd., Montebello; (213) 722-3976) including a pair of unusual vines. Mexican flame vine ( Senecio confusus ) bears deep red-orange daisies and makes a terrific show if allowed to climb into a yellow-flowered tree such as thevetia or cassia. From the very dry north end of the Yucatan Peninsula comes Montanoa schottii, a viney shrub covered with sparkling white daisies in fall and winter that excels at covering chain-link fences.
The best known tropical shrubs for water-conserving gardens are the hybrid lantanas, famous for their wide color range, long bloom period and easy care. A number of shrubs growing wild with lantanas in the American tropics also make adaptable garden plants. Yellow bells ( Tecoma stans ), pride of Barbados ( Caesalpinia pulcherrima ) and Trinidad flame bush ( Calliandra tweedii ) are some of the choices that combine the fiery colors of the tropics with good tolerance to heat and drought.
There are some key differences between plants from the dry tropics and other water-conserving plants that influence when and where to plant them. Most important, tropicals are more tender to frost. A few, including Mexican flame vine, are damaged at 32 degrees, but most can withstand temperatures down to the 25-28 degree range.
Even when frozen to the ground, established plants recover quickly when growth resumes in the spring. Recently planted specimens are most susceptible to frost, so tropicals are planted in spring to give them a chance to become established before their first winter. This contrasts with the fall planting recommended for most water-conserving plants.
Another important difference is that water-conserving tropicals are adapted to summer rain, a rare commodity in Southern California. They are no match for California natives for strictly unirrigated, summer-dry parts of the garden. Instead, use tropicals where they can receive careful watering for their first two summers in the ground and thereafter soakings at 2-3 week intervals in summer. If tropical plants become too dry they will stop blooming and eventually will start to shed their leaves in response to prolonged drought. Once watered they quickly leaf out and resume blooming.
Perhaps the most welcome difference between tropicals and other water-conserving plants is that many of them bloom in summer--a characteristic sadly lacking in our native chaparral flora. As water becomes scarcer, plants from the dry tropics will help maintain the 12 months of color that is the birthright of every Southern California gardener.
