Summertime Watering (Revision of 7/6/09 blog post)

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It is a hot day. As I sit down to write this article on summer garden care, I decide to check the temperature. It is 84 degrees Fahrenheit at 4 PM (7/6/09). Many garden gurus urge you to get out there and water your plants when it is this hot and dry. This recommendation, however, is based on the underlying assumption that plants in your garden are growing actively in the warm season. This is true for much of the country, but it is not the case for many native plant gardens here in California.

Annual wild sunflowers (Helianthus annuus) and deer grass (Muhlenbergia rigens) keep my summer native garden looking lush through most of the summer. By late August everything looks pretty dry until temps moderate and we get some moisture. (July 31, 2022)

Summertime is sleep time in Southern California

Summer in Southern California is similar to the winter in the rest of the country. Colors are subdued and plants are slowing down, even going dormant. This is an adaptation to our climate. To make it through the more than six months with no rain and high temperatures, not only do plants slow down but they have also developed many other adaptations. For example, waxy leaves reduce water loss, white hairs reflect sunlight and capture fog and dew, and extensive root systems suck up as much water as possible. Some plants are annuals. These complete their life cycle in one year. The seeds germinate when the rains start in winter, they flower in early spring and produce seeds in the late spring. The seeds then wait out the dry season and start the cycle again when conditions are right.

Water to meet your plants’ needs

As the heat turns on and California native plants slow down, so should your watering. However, during a plant’s first few years in your garden, anywhere from one to three, you must check it often. Water it enough to keep it going, since its root system is not fully developed, yet not so much that it puts on unsustainable, excess growth, or succumbs to fungal and bacterial diseases. It is a bit of a balancing act and requires that you pay attention to your plants. As your garden matures, it requires less water and less scrutiny. Depending on your plant choices, areas with established plants can be watered about once a month or less during the summer. Some plants like flannel bush (Fremontodendron species), should get no summer water at all.

Because conditions vary from garden to garden, and even within gardens, the best irrigation schedule is determined by watching your plants. In my garden, I manually set each zone on the controller for my front yard. Most of the yard, though, is no longer on an irrigation system. Beds with new plants receive water about twice a month, although this depends entirely on how they look. If they are drooping and the soil near their roots is dry, I water them, making sure that the entire root system gets wet.

Coastal gum plant (Grindellia stricta var. venulosa), July 3, 2009. Although this lovely plant grows and blooms in summer, its waxy leaves help it retain as much water as possible.

Some watering tips

It is best to water before a heat wave occurs. This is because plants tend to slow or even shut down when temperatures are very high. Therefore, they may be unable to take up water and transport it to their leaves. So be sure to water before the heat turns on.

In addition, water early in the day when the soil is coolest. There are several reasons for this. First, disease-causing microorganisms grow more slowly in cooler soil. Second, as mentioned above, plants are better able to take up water when it is cooler. Third, less water is lost to evaporation. Here in Southern California, and I suspect elsewhere too, not only are afternoons hot, but the winds pick up late in the day. So cool, still mornings are best to ensure that the water goes to your plants and doesn’t just evaporate. And finally, snails and slugs love moist soils. If you water at night, the slimy creatures will be busy in the early morning munching on your young plants.

Remember to water only those plants that need it. Water by hand new plants that are placed among established ones. And if you are hand watering, check the soil to be sure that it is getting moist several inches down. It is always surprising to me how long it takes for water to infiltrate into dry soil. This is especially true if there is organic mulch covering the soil.

Speaking of new plants, I sometimes throw a sheet or shade cloth over sensitive plants when the temps hit triple digits. This is helpful for young plants and established fruit trees. Do not rush to remove damaged leaves if they burn during an extended heat wave. They provide some shade for the lower leaves, and it is hard to tell what will recover and what won’t.

For more information on summer gardening during a heat wave check out the following posts:

Walking through the garden in the late afternoon heat, I am tempted to water a four year old sage, but I remind myself that it is hot and tired, and it does not want a shower, it wants to sleep until it cools down.

2 thoughts on “Summertime Watering (Revision of 7/6/09 blog post)

  1. Barbara,<br /><br />Great article on watering natives. We have been in a drought for 4 years now, some plants have thrived others have disappeared. These fire dept. orders must be a pain, but good for not burning down the neighborhood. Our hard clayish soil gets 1/2 to 3/4 inch wide cracks in it. We have rain barrels for the garden. Saw 6 rain barrels in a row on a platform the other day fed by

  2. Yes, watering new plants is a conundrum, isn&#39;t it? I had a major breakage in my front garden, where everything is new. I&#39;m watering everything by hand about once a week, trying to do it early in the morning. We&#39;ll see how it goes, but it&#39;s enjoyable to be out there.

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