Summer watering

Watering natives in the summer may require some manual adjustments

Some of us get into a fixed pattern of watering our plants - and then the weather throws us for a loop. Summer watering is the most difficult to judge. Right now is a bad time to keep to that fixed watering pattern. The hot, muggy water can cause problems: under-watering will stress plants, but over-watering in hot soils can cause pathogens to flourish. 



There used to be a "rule of thumb" that went like this: "once a week the first summer, once every two weeks the second summer etc." but this can also lead us astray. Instead, focus on watering to keep the plants alive and notice each particular micro-climante in your garden to differentiate needs, based on soil types, wind, sun exposure and specific plants.

Native Again Landscaping put together this guide: 

Tree of Life Nursery provides this guide. 

RSABG says this at their web site:

Water may be the problem
Water (either too little, too much or at the wrong time) is a primary cause of death for garden plants. To figure out what is going on you should start by checking the soil. If it is damp where the roots are, then over watering or watering when the soil is warm may be the culprit. Watering warm soil creates conditions that support the growth of pathogenic bacteria and fungi. Native plants adapted to dry summers are especially susceptible to these pathogens. Water is present but the plant can not absorb it due to root damage. These plants usually do not recover. The only thing you can do is cut the water, let the soil dry out and see what happens.

If the soil is dry and the plant perks up when watered, it was thirsty due to too little water. Water deeply and hope it was not too stressed to recover. Be aware that some plants will droop during the heat of the day but recover as temperatures cool down. As long as they perk up when the sun goes down, hold off on water.

Young plants, those not yet established, are most vulnerable during severe weather. Their small size and undeveloped root systems make it hard for them to survive weeks of extreme heat. Yet, water and warm soil often lead to root rot. So it seems that watering is bad and withholding water is bad. Observing your plants carefully—looking at the leaves, both old and young and the buds—can tell you a lot about what they need. When old leaves turn yellow and drop, this may just be part of your plant’s normal seasonal cycle. It is common in sages, monkey flowers and some Ceanothus. When the younger leaves and buds dry up, you probably have a problem. If the whole plant wilts, this is a bad sign as well. When stem tips and leaves droop slightly the plant most likely needs water. If you must irrigate in the summer, try to do it when the soil is cool, such as early morning or on foggy, cool days.

Your garden

So, how to figure out your needs? Start with the soil. Many of our most popularSouthern California natives require excellent drainage. The classic chaparral profile (gravelly or sandy soil on hillsides with a sprinkling of leaf litter) provides that fast-draiingin profile we all read about. 

But in many spots in the county, we garden in clay soils. So there is an automatic mismatch.  Roots need air in the soil. Clay soils provide less of this and the water taht does absorb into clay soils stays longer in the site. This drainage profile and constant warm wet soil in the hot season promotes overgrowth of soil fungi and results in water mold fungi diseases that eventually kill many trees. 

If you have clay or clay loam soils, you will need to water infrequently, slowly, and deeply in order to allow air to penetrate, and then to wick away. If you still have problems with late summer plant death, then consider installing new plants in a mound of soil to provide the good drainage most native plants prefer. 

Pete Villeaux from the Bay Area says, "The simplest method to use for determining whether and when a plant should be watered is the finger test. I feel like a broken record about this, but it really works in all situations: stick your finger in the soil next to the plant – 2-3” down into the soil. If it feels moist, there’s no need to water. If it feels dry, then you can water in most cases.  Once again, the exceptions are those plants which are most sensitive to summer water – fremontodendron, small-leaved ceanothi."

If your finger isn't that sensitive, or your soil is dense clay that won't allow for the "digital" water meter, try using a moisture meter. If the plant is newly installed, probe in the place around the interface between the original soil in the pot and the native soil in your garden.