rain in the garden

Mild winters have brought so many people to Southern California that there is not enough water – thanks to those same mild winters – to sustain them and their gardens.
Were it not for snow and rivers far to the north, most of us wouldn’t be in Los Angeles, and neither would our plants. But increasingly, people are planting species such as ceanothus, manzanita, rosemary and lavender, which can survive on winter rain plus an occasional deep soaking in summer.
Winter rain is important not only for giving plants a ready supply of water when growth resumes in the spring, but it also leaches harmful salts, which accumulate during the summer, out of the soil.
Last spring, following the wettest winter in years, trees bloomed with an unprecedented abundance of flowers. Evergreen pears were covered with white blossoms; roses never looked so good; record crops on fruit trees were reported.
An old silver maple tree I had observed for five springs produced flowers and seeds for the first time.
Why couldn’t irrigation, you might ask, produce the same effects as rain? Irrigation has two problems. First, it never is applied evenly; the root zone of a plant never is supplied uniformly with water except by rain. Second, our irrigation water contains salts that, when built up in the soil over a long period of time, are deleterious to plant growth. Only rain water can dilute these salts and drain them away from plant roots.
The Japanese maple is a plant that is hypersensitive to salt; the tips of its leaves nearly always are fringed in brown, the classic symptom of salt stress. Many species of palms, whether for indoor or outdoor use, also are
salt sensitive.
Cold, like rain, is necessary to the success of many garden plants, particularly edibles. Starch turns to sugar in cold weather and winter peas will be that much sweeter for a few extra-cold nights.
Each type of deciduous fruit tree has a different cold requirement for flower production. Cherries, for instance, require more than 1,000 hours of winter chill – hours below 45 degrees Fahrenheit – to produce fruit, which is why you can have a cherry orchard in Lancaster but not in Van Nuys. Lilacs, the favorite spring bloomers back east, will flower sparingly, if at all, following a winter as warm as we have experienced this year.
Winter pruning of roses should be done during the next two weeks. Cut back your rose canes just before buds begin to swell.
On hybrid teas, canes can be cut back to a height of 18 to 36 inches, depending on the size and number of flowers you want next year. The farther you cut back, the larger your flowers will be. If you cut back less, you will produce more flowers, but they will be smaller than if you had pruned more severely.
Like hybrid teas, all modern roses – polyanthas, floribundas, grandifloras and miniatures – flower on new spring growth, and a fairly vigorous pruning is necessary to maximize bloom. The same applies to tree roses, which usually are hybrid teas or floribundas.
Old roses – such as rugosas, gallicas and damasks – do not require such vigorous pruning. Overgrown canes can be cut back by one-third, and others lightly tipped. Climbing roses bloom only at the ends of vertically growing shoots, but if these shoots are bent horizontally, they will bloom along their entire length. On any rose, be sure to remove suckers growing from the base, and dead, diseased or spindly growth.
It should be remembered that old roses tend to bloom once, or perhaps twice, a year. Unlike the modern hybrids, however, they are quite resistant to insect pests and mildew.
It is worth experimenting with old roses, which require far less maintenance than hybrids and have a character all their own. The rugosa rose, for instance, has a dark green, leathery leaf that adds a uniquely decorative touch to any garden.