Watering Native Plants in Winter

One of the benefits of living in Southern California is not having to water during winter.  In many years, rain supplies most/all of our garden needs from November or December until April.   But this year (2011-12) is not a usual year.  La Nina conditions have produced a winter with very little rain.  And the rains we’ve gotten have been widely spaced – with plenty of warm windy weather in between.   In short, our soils are very dry for this time of year.  

The mediterranean climate in Gardena CA is characterized by relatively mild, rainy winters and a long dry summer/fall.   Our climate is a result of our location - near 35º N latitude and on the western coast of North America.  Prevailing winds blow off the ocean in winter/spring and from the dry lands to the east in summer/fall.  We share a mediterranean climate with several other parts of the world - the Mediterranean region itself, the South African Cape, the west/south coast of Australia and central coastal Chile.   All share a similar geographic location; their plants show similarities as well.

Southern California’s native plants have a number of strategies to cope with long dry periods (more on that topic in the coming months).  But local native plants – even those that need no summer water – rely on adequate winter rains.   Winter is the time that many native plants grow, develop deeper roots and obtain needed nutrients from the soil.  All this requires moist soils.  And if Mother Nature doesn’t provide, then we need to supply the water ourselves (unless we prefer to let nature take its course).   In Mother Nature’s Garden, we’re watching the weather forecast closely and watering our newly installed garden.

Many native plant gardeners have questions about winter watering.   Since we often have dry periods – even in a normal winter – it can be difficult to know when/how much to water.  A good rule of thumb is to check your soils if we’ve had 3 weeks of dry winter weather.  Even though plants appear vigorous, their supply of soil water may be getting low.  Dig down 3-4 inches into the soil to check.  Be sure to clear away the mulch and dig down into the soil itself.  If the soil is dry at the 4 inch depth, it’s time to water. 

The best time to water is on a cool cloudy day, imitating Mother Nature.   Check your weather forecast to choose an appropriate day.   Then water either in the early morning or late afternoon/evening – both are times when winter rains would normally fall.   If your garden has drip irrigation or soaker hoses you can easily provide a slow supply of water that can infiltrate the soil. 

If you’re watering with overhead sprinklers or with a hose/sprinkler, you may need to break up your watering into several sessions to allow the water to soak in.   In general, you want to supply water at a slow rate over a long enough period to replenish the soil. The length of time will depend on your soil characteristics.  The only way you’ll know if your soil is moist (but not soggy) is by digging down and checking. 

While watering your native plants in a dry winter may seem wasteful, remember this: giving your plants adequate water now will allow them to survive the coming dry summer, when water will really be in short supply.   If you still have qualms about winter watering, you can choose not to water – the choice is yours.  The hardiest mature plants will likely survive, just as they do in nature.   Your garden will most likely change, but change is a fact of life – both in nature and in our gardens.