UNITED STATES—All the optimistic predictions of a rainy winter do not help with the drought yet. Nice warm weather only makes the garden even drier. Many of us have let our lawns dry out, maybe with plans to replace them later. Some have decided to replace lawn with artificial turf, hardscape or other landscape features.

The problem with this is that trees and other large plants that have dispersed their roots under the lawns are thirsty for the volumes of water that they had gotten while the lawns were well watered. They can survive longer than lawn does without watering, and will adapt to less water when they do get it, but they can not do without water completely.

It seems silly to water artificial turf or new decking, but it is sometimes necessary, especially for thirsty trees like willow, ash, elm and redwood. This is why some artificial lawns are outfitted with the original irrigation systems of the lawns that they replaced.

Drought tolerant trees, like certain oaks and most eucalypti, are more adaptable. Of course, those that were originally watered generously are greedier. Those that got only minimal watering may not notice if they get none at all. Regardless of their requirements, they all can be watered less frequently than lawns were, but should be watered generously when they do get watered.

Generous, but infrequent watering soaks into the ground better to satisfy deep roots. It is actually what most trees prefer. Lawn needs frequent watering only because the roots are so shallow. Generous, but infrequent watering uses less water not only because less evaporates from the surface of the soil, but also because less water gets used.

For example, watering weekly for 20 minutes is a generous volume of water, but is still less than watering for 15 minutes three times each week. It is only 20 minutes of watering compared to forty five minutes of watering.

Highlight: plumbago

There are not many flowers as blue as those of plumbago, Ceratostigma plumbaginoides. Individual flowers are not much more than half an inch long, but can be quite abundant until autumn. Each of the many terminal flower clusters is on a rather reliable schedule, so that new flowers begin to open as older flowers begin to fade.

Thin stems stand only about half a foot to a foot above underground rhizomes. Individual plants get about 3-feet wide, but realistically, will slowly spread farther if conditions are right. They do not spread fast enough to be invasive, but can get into some unexpected spots if not controlled. The simple leaves are about two inches long.

The main problem with plumbago is that it is deciduous, so it dies back to the ground in autumn. The weather is too mild here to produce the good fall color seen where autumns are cooler. Plumbago is a popular bulb cover because new growth, although slow to develop, emerges just in time to obscure fading foliage of early spring bulbs like daffodil and tulip.

Plumbago also works well with stone, since the stone is still appealing without the foliage through winter. The wiry stems weave nicely through otherwise bare cobbles, or spill slightly over low stone walls. Even though shade inhibits bloom, plumbago makes a nice informal ground cover under open shrubbery.