Improper watering is one of the biggest reasons for plant failure. In fact, over-watering, especially while native plants are not actively growing during the hot summer months, is a major problem. On the other hand, we often forget that many California native plants do most of their growing during the cooler, damper winter weather. A slight misting or a little drizzle will not provide enough water. This is especially true for young, unestablished plants, but even mature plants benefit from infrequent, deep watering during dry winters. If we do not get a good soaking rain for more than a couple of weeks, you may need to provide supplemental irrigation.
After planting natives during the winter season—the best time to plant in Southern California—it is important to water your new plants thoroughly to make sure that they settle in and their roots are completely wet. Through the first season your plants should not be allowed to dry out totally. Water well and then allow them to dry partially. If the plant is drooping and the soil is dry be sure to water immediately.
The roots of plants absorb water in the form of vapor from pockets in the soil. For this reason it is best for the soil to be watered thoroughly and then allowed to dry. A thorough watering ensures that the entire root ball receives water. Allowing the soil to dry creates good conditions for the absorption of water by the root hairs, and it reduces the likelihood of root rots from soil pathogens.
Get to know your plants and your garden conditions by checking your garden often. Dig down a few inches and feel the soil to determine whether your plants need water. Observe your plants so that you can tell when they are thirsty before they become too stressed.