THE COASTAL GARDENER:Timing is everything if you’re a plant

Today’s sunlight will last 10 hours and 30 minutes; tomorrow’s, 10 hours and 31 minutes. Tonight’s temperate will bottom out at 48 degrees. The temperature of the soil six inches below the surface will average 63 degrees today.

The length of a day and its temperatures are usually a mere curiosity to humans. Plants, however, respond to them in very precise and predictable ways, completely indifferent to the wants and whims of a gardener. Beginning gardeners, unaware of the “rules” of the game, may challenge nature by planting at the wrong season or in the wrong climate. In a battle of nature versus the gardener, nature almost always will prevail.

Understanding nature’s signals and submitting to them, rather than fighting against them, is the sign of a mature and experienced gardener.

The month of March in our coastal garden is ripe with opportunity and is an active time for a gardener. A few subtleties of timing, however, can make your experience more successful.

In the vegetable garden, it is almost time to set out tomato transplants — but not yet. The soil is still too cool. More important, tomatoes set into the garden now will not produce fruit any sooner than those set out a month from now, so why rush? Tomato fruit will not set until night temperatures stay above 55 degrees for at least two nights in a row. While you’re waiting, plant a quick crop of loose-leaf lettuce. You’ll harvest the lettuce just in time for the perfect tomato planting time.

Annual flowering plants don’t need to set fruit, so night temperatures are not quite as important. Instead, gardening success with these plants will be more dependant upon soil and air temperatures. Spring flowers that I find ideal to plant right now in our still cool soil include petunias, pansies and violas, bacopa, nemesia, snapdragons, lobelia, ageratum, cosmos and schizanthus.

Impatiens and begonias need warmer soil than March affords, although thousands of gardeners will push the rules and plant them early. Not much harm will be done by planting now, but they will tend to languish and sulk in the still too-cool soil. The same is true for verbena, dahlia and marigold. Don’t even consider coleus, zinnia, gomphrena and lisianthus for another month or two, as they need even warmer soil.

Gladiolus, tuberous begonias, perennial dahlias, most lilies and a few other plants that grow from bulbs, corms, rhizomes and other underground organs should be started right now. The lower air temperatures and the mild soil temperatures are perfect for their initiation of roots, followed by foliage and ultimately flowers.

Start feeding citrus and avocadoes right away. Citruses, especially, are heavy users of nitrogen and micronutrients. So-called minor elements, such as iron, zinc and manganese, are often absent from synthetic fertilizers — another reason why I recommend organic nutrition. While you’re at it, be sure to apply fertilizer to most potted plants. The soil of potted plants will warm considerably earlier than that of the ground, requiring more and earlier nutrition, and resulting in an earlier season of foliage and flowers.

If you’ve been pinching the tips of your fuchsia over the past three months, as I’ve recommended, it’s time to stop. Your pinching diligence has developed a very full plant with lots of growth tips. Now, stop pinching, feed it with a balanced fertilizer and let it bloom. It will be spectacular in about six weeks, with hundreds of blooms.

If you’ve been considering removing some of your thirsty exotic plants and replacing them with native plants, it’s too late. California natives are perfectly evolved to grow quickly during the rainy season, then slow down or stop growing during the dry summer months. Planted now, toward the end of their growing cycle, they will not have a chance to root and establish themselves. Mark you calendar and start making plans to do your native planting this fall or early winter.

During March, you can still convert portions of your garden to a low-maintenance, thirst-quenched “California friendly” plant palette. Other than our native plants, many low-water choices can be added now. Check with a knowledgeable nursery horticulturist for specific recommendations.

Following Orange County’s coldest winter in nearly 20 years, many gardeners are eager to replace their frozen plants with new ones. Hibiscus, bougainvillea, lantana, cuphea, carissa and dozens of others were likely damaged in your garden. In spite of your eagerness, these are tropical plants that need warm soil, long days and higher temperatures to grow. This is not the time to plant tropicals; wait a couple more months.

Those are some “rules.” In nature it’s hard to cheat. Abide by nature’s rules and you’ll have a more successful and rewarding garden.

ASK RON

I have a grapefruit tree that my father started 25 years ago from a fat Harry & David fruit seed. It is now about 20 feet tall. About three years ago, it simply exploded, producing well over 100 rather seedy fruit. But ever since then it has had very, very few blossoms and fruit; maybe five or so. What do you think? Can I bring it back into flower, or has it simply turned into an ornamental?

DAVE BLACK

This is the pitfall of growing a hybrid plant from a seed — you do not get a carbon copy of the mother plant. Almost always, the seed progeny is an inferior and undesirable plant. Citrus hybrids, as well as avocado and many other plants, can only be reproduced by vegetative means; cuttings, grafting or layering. There is probably nothing culturally that you can do to make this plant behave any differently. It is the genetics of the grapefruit. Enjoy your shade tree.