by Charlene Burgi
Several calls came into my office this past week regarding the need to irrigate. I wish there was a blanket answer I could share. I could give a different answer for every call and every garden.
Our gardens are as unique as our Marin County environment. Living next to the Bay is much different than living in Lucas Valley or nestled in the redwoods of Mill Valley. Diverse microclimates can be found throughout the county and also within our individual gardens. The microclimates may be less dramatic in our gardens, but they require our attention, especially when it comes time to water our plants.
Last Sunday, the temperatures reached close to—if not over—80 in some parts of Marin. Living in the far north part of the county, I pulled out my trusty soil probe to check a few locations around the garden. Each plug I pulled showed considerable moisture in the root zone. The smart controller on the property knew not to water. However, my potted plants looked a bit droopy and the index finger test* showed they needed water. These pots are exposed to the sun and air, and the roots growing in them dry out faster than if they were in the ground. *Index finger test: Using your pointer finger, insert finger into the soil to the depth of the second knuckle. If the soil feels dry, water. If the soil is too hard to penetrate, amend the soil by repotting!
Soil conditions and mulch (or lack thereof) can greatly determine the water-holding capacity of the soil. Chances are you won’t need to irrigate as often if you have worked compost and soil amendments into the garden. The enriched soil becomes a living sponge that not only retains water but provides life-supporting elements to keep your plants and soil healthy. Add several inches of organic mulch to the garden to further reduce the surface soil evaporation.
Plants are another huge factor determining the need to irrigate. Do you have a garden of native plants, or acres of lawn and other high-water-use plants? Are the plants in the shade or against a reflected heat source such as a south-facing window? Are you forcing a plant to grow outside its “comfort zone” and providing extra water to keep it alive? The list goes on. For each scenario you will find a different answer whether to irrigate or not.
With all that in mind, before overriding your irrigation controller or turning on the hose, please test for the moisture content in your garden. Look for wilting plants. And while walking about, write a to-do list of what can be done to improve the living conditions of your plants. Consider the pleasure the landscape brings to you and see what you can do to give back.