It Is So Hot! Do I Water or Not?

It is a very hot day. As I sit down to write this article on summer garden care, I decide to check the temperature. It is 4 PM and currently 93 degrees Fahrenheit. Something on the weather website (www.weather.com) catches my eye. There is a watering needs index that states that we are currently at a “Very High Watering Need.” The legend explains “It is very dry and watering is necessary.” This recommendation is based on temperature and precipitation, and indeed, it is hot and dry! The underlying assumption is that our gardens are populated with plants that grow 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.

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 long, dry season. To make it through the more than six months with no rain and high temperatures plants have developed many other adaptations too, including waxy leaves to reduce water loss, white hairs to reflect sunlight and capture fog and dew, and extensive root systems. Some plants are annuals that complete their life cycle in one year, producing seeds in the spring that await more hospitable conditions to germinate and begin again.

As the heat turns on and California native plants slow down, so should your watering. 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. As your garden matures, it requires less attention. 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. Beds with new plants receive water approximately once a week, 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. New plants placed among established natives are watered by hand, as needed.

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