As the heat kicks on, its important to think about the life that cannot move away from it. Organisms with no respite from the midday sun need our help! Plants cannot move out of the heat! So, during these periods of extreme heat, they need help staying hydrated and we need them to survive.
So what can be done to assist the foundation of our life support system during heat waves? Number one is giving them water. Deep watering of the root zone 24-48 hours in advance of extreme heat reduces heat stress in plants and keeps them thriving. Irrigation water needs to penetrate the ground and ideally meet the natural moisture table still present from winter and spring precipitation. Shallow watering that only wets the soil surface can result in permanent stunting of young plants. This kind of superficial irrigation is akin to training a child to walk on her hands instead of her feet. The roots, i.e. legs of the plant, will turn upward and never be able to access the water and nutrients deeper in the soil.
Deep watering in advance is all that healthy, established plants and trees need to handle the heat. However, young plants without established roots often require water throughout the heat wave. While drip irrigation under a layer of mulch is an efficient way to irrigate plants, it doesn’t always put the water in the tiny root zone of young transplants. Therefore, overhead watering with a hose or sprinkler may be required in order to keep young plants healthy. Please, DO NOT BE AFRAID to water your wilted plants during the middle of the day. There is NO basis in the myth that water on the leaves during midday will burn plant tissues. Not watering wilted young plants at midday is like depriving a panting dog of water. Water is required for life, it will not hurt the plants or the dog. If you persist in thinking that midday watering will harm plants, please review this short article on leaf scorch (1).
Maintaining moisture around plants throughout the day not only keeps them hydrated but also cools them. Water’s phase change from liquid to gas, evaporation, is the most important method of cooling the environment. Once the moisture is gone from the system it will reach deadly temperatures in short order. We can prevent heat assassination by mulching our plantings. Wood chips of any kind are an excellent, locally available mulch that can save plant lives. Moist, porous, non-homogenous wood chip mulch allows evaporation to cool the air while maintaining soil moisture in the root zone. If you are concerned about mixed species wood chip mulch because of pathogens, nitrogen stealing or other perceived issues, please take a look at this pamphlet from the University of Washington (2).
Water is not just a key component in all living organisms, it is life itself. We all want to go on living so we can enjoy another day here on this beautiful aqua-marine planet. Plants are the basis of our life support system, but they are stationary, so it is up to us to supply them with the water they need to sustain themselves through extreme heat. Our future thrival depends on keeping plants hydrated. Even at mid-day in 100 degree heat, the future starts now.
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