Watering Native Desert Plants0
Water regularly in cool months; less frequently, but deeply in hot months.
One of the biggest advantages of using California native plants is that you can select plants whose water needs match our climate. California native plants are well adapted to our climate and can tolerate extended periods of heat and drought. Many California natives in the wild experience a drought-induced dormancy in the summer. They simply maintain their size and shape, add very little or no new growth, and sometimes even lose a few leaves toward the end of the season. This is how they “tough it out.” For natives to display such resilience during our long, hot, rainless season, they need to be well-established with extensive, deep root systems. You can help them establish deep roots by irrigating them properly with deep, infrequent watering.
To have well-established plants in the summer, it is best to plant in the fall to spring planting window. Summer is the most difficult season to install native plants in the landscape. Wait until fall if at all possible and you will decrease the amount of irrigation needed to establish native plants over their first few years. You may successfully plant natives any time from fall until spring, but they will require less water to become well-established the earlier they are planted in the fall-to-spring planting window.
How Much Water?
You can kill natives with too much water, especially during summer months. In general, California’s arid natives in both the low and high desert get significant rainfall only during winter rains. To establish a newly-planted native plant, check every 3-4 days, and water regularly whenever the soil in the root zone (about 3-4 inches deep) dries out.
Since moisture retention varies with soil texture, season, and sun-exposure, you will need to establish the frequency at your site by testing the soil around new plantings with your finger or a moisture probe. Branches which shade the root zone and leaf litter or mulch will protect the topsoil from excessive drying, and extend time between watering.
- Water to keep the plant alive, not to make it grow fast. Try to teach the plant to be drought tolerant. Watering less often and more deeply will stimulate roots to grow deeper instead of near the surface where they will be susceptible to drying out.
- Water by hose, drip or low volume sprinkler in early morning. Drip tubing fitted with microspray emitters deliver water in a more natural way (more like rainfall) than drippers. Install two half-spray emitters per plant, at the drip line of the plant (under the outermost ends of branches), each pointing away from the plant. As the plant grows, move the microsprays away from the plant, keeping them at the drip line of the plant. Avoid watering during the heat of the day or at night as this may cause branch die-back or root rot. Remember if water runs off or does not soak in it does not count.
- Water only when the soil in the root zone begins to dry out. Check the root ball 3-4 inches below the surface to see if it is moist; if it is still moist, wait for the root ball at that depth to dry out between watering days. Water enough to thoroughly soak the soil around the plant, and deep enough to reach the bottom of the planting hole. The establishment period for most natives is usually one year. Your soil type will determine how often you water.
- Water regularly in cool months if no rain falls. Water less frequently but deeply in hot months. Desert soils that remain consistently wet during hot summer months are prone to the growth of harmful soil pathogens, bacteria, and fungus, which can cause root rot in native plants and quickly kill them. Remember that our desert native plants have evolved to survive in wet soil when it is cool, and dry soil when it is hot. They are not adapted to survive wet, HOT soils. If you are able to add water only at a depth where the soil remains cool even in the summer (using a deep-water sleeve, with no water moistening the hot surface soils), then you may safely irrigate throughout the summer.
- Avoid watering frequently with small amounts of water (high frequency, short duration). This method only teaches roots to stay at the surface, making them susceptible to the moisture loss of hot, quick-drying surface soils, and compromising any drought-tolerance they are capable of achieving.
- Apply water at a low frequency with long durations to thoroughly soak the soil and allow vital oxygen to re-enter the root zone between watering. Remember, mulch on the surface will preserve soil moisture between watering.
- For best results, avoid using overhead irrigation for long durations (especially in the sun) because prolonged leaf-wetting during the dry season can promote disease.
Once your plants are established you may only need to water them occasionally during dry winters and once a month or less during the dry season—late spring through fall—to keep them looking good. If you must water them, try to simulate a summer thunderstorm: soak the soil well but very infrequently.