If you've planted drought-resistant natives recently, dry spells during the wet season are the most crucial time to be out in the garden. You want your natives to get ample water so they can grow deep roots while the soil is cool, so that when they are established, they will be able to find their own water during the long dry season.
Most natives are established after two or three summers, or when they have doubled or tripled in size. Putting most of their energy into root growth for their first couple years in a new location means that some natives may not put on much top growth at first. It's all happening underground.
To expand into the surrounding soil, the root balls need to be moist. As the rainy season progresses, check the soil as well as the root ball weekly during dry spells to make sure it's moist. You can poke your finger in the soil, or use a moisture meter to go deeper. Don't flood the plant if the root ball is already moist.
If your plants are mulched, make sure the water is getting down to the soil and root ball. Some mulch can absorb a surprising amount of water, leaving the soil underneath dry, before it's saturated enough for water to seep through.
To get a better sense of what the soil feels like and looks like at different moisture-meter readings, put your garden soil in several gallon pots and water it different amounts Notice that clay soils must be watered slowly for the water to be absorbed. Shallow, frequent watering may not reach the root ball at all.
If rainfall is below average by the end of January, this is a good time of year to mimic a good soaking rain by, for instance, setting up sprinklers for 6 hours. You can do this once a month until April.
During the rainy season, pay attention to plants under the eaves or under large, spreading evergreens such as deodar cedars. Often these plants don't get any water in the rainy season unless the wind blows the rain around, or unless a soaking rain drenches everything.
Once the dry season begins, the plants need only enough water to keep them alive. Water in warm soil fosters the growth of fungi that cause root rot and crown rot. After the spring rains end, continue to monitor your plants closely. Young plants may still need supplemental water for their first two or three summers.
For new plantings, water both the plant and the planting area well just before you plant, allow them to drain, then water thoroughly. Make sure the plant's crown is slightly above the surface of the soil so that water will not collect there and precipitate crown rot.
An alternative is the “planting in mud” method described in last July's column. Remember that it has had a high success rate for California lilacs, currants and gooseberries, native buckwheats, sages, and fremontodendrons. It's not recommended for manzanitas.
Thorough winter watering is less crucial for plants that need and can tolerate water year-round, such as riparian plants.
© 2009 Tanya Kucak