GARDENING : MORNING GLORY JOY IN FULL BLOOM.

Byline: Joshua Siskin

A few days ago, my Mauritanian morning glory started to bloom. This is a plant that is hard to resist when you see it in full flower. It has miniature gramophone-shaped flowers of a violet blue, which open up in profusion from among nearly circular sea-green leaves. It is a mounding, trailing plant that spills over my front walkway; it will tumble out of your terra cotta or ceramic pot just as well - as long as it is reached by most of the day's sun.

Normally, the Mauritanian morning glory (Convolvulus mauritanicus) blooms in late spring or early summer. This year, many perennial plants have flowered before their customary bloom time. Also numbered among the early bloomers in my garden are Jerusalem sage (Phlomis fruticosa), a dwarf Peruvian lily (Alstroemeria), and cape fuchsia (Phygelius aequalis). I should add that these plants were blooming prior to the onset of our unusually cold and rainy April weather.

Many reasons could be offered for early flowering of plants in Los Angeles this year. Excepting a late December freeze, this past winter was warmer than most. This winter was also unusually dry. Although rain finally came in April, the long period of dryness that preceded it forced plants into early flowering, which is a typical response to drought stress. My disinclination to water indiscriminately - that is, my preference for watering by hose as opposed to sprinkler irrigation - ensured that my plants got just the amount of water they needed to grow; excessive watering may have led to excessive leaf growth at the expense of flower development.

It is a short jump from wondering why plants are blooming now, rather than later, to wondering why flowers of certain plants open early, rather than later, in the day. The morning glory, as you may have guessed, was given its name because of its tendency to bloom in the morning hours and to fade or close up in the afternoon. Please note that this blooming habit does not apply to my perennial morning glory but to its famous relative, the far more renowned annual vining morning glory, the one with large blue or purple funnel flowers. The vining morning glory actually may be more infamous than famous on account of its invasiveness. Not only will it smother surrounding plants in the course of a single summer, its seeds will sprout the following year in such abundance that you may as well regard it as a weed - a weed with magnificent flowers, but a weed nevertheless.

There are quite a few plants that flower only in the morning, such as gazanias, the annual moss rose (Portulaca grandiflora), and certain tropical orchids such as vanilla (Vanilla planifolia), which produces the vanilla beans used in ice cream and other confections.

Other plants, such as the four o'clock (Mirabilis jalapa), open their flowers in the afternoon, and still others open their flowers in the evening, including night blooming jasmine (Cestrum nocturnum) and the California native evening primrose (Oenothera Hookeri).

Various theories have been advanced to explain why some flowers open in the morning, some in the afternoon, and others in the evening. The most popular theory suggests that temperature change is the signal to which flowers respond, where both their opening and their closing are concerned. For example, when grown indoors, gazanias are found to keep their flowers open around the clock; this phenomenon is explained by the relatively small temperature changes that occur inside the house. Outside, gazania flowers are only open from morning until dusk and do not open at all on overcast days.

It is nothing more than a happy accident that I planted Mauritanian morning glory in close proximity to plants with flowers that contrast nicely with its own. The violet blue of mounding morning glory shows up well against the butter yellow of Jerusalem sage, the rose pink of Peruvian lily, and the deep scarlet of red cestrum (Cestrum elegans). Yet, I must confess to a certain color blindness where flowers of garden plants are concerned. As long as ornamental plants are growing healthily together, it seems inevitable that they should complement each other aesthetically as well.