PSA #1: Trees still need water over the summer and fall, just not as much as you might think
Autumn 2021. California is drought stricken. Wildfires seem endless. Fire season. Our state is at the precipice, where we are collectively holding our breath hoping fires will not enflame when our Diablo and Santa Ana Winds blast regionally-scaled hair dryers throughout the north and south lands, respectively. We wait, but there is something we can be doing that takes a modicum of water, preferably from recycled sources. Save our withering urban trees. Hydrate them to lessen the damage and risk.
This is the time to be truly observant of the landscape around you. Survival of the fittest is occurring right in front of our eyes. You will see numerous trees still thriving despite drought. Take note of the successful species. By their very nature, they store water in their systems and conserve with slow moisture release through what is called transpiration. Our California native trees succeed at performing this conservation, just as so many other trees originating from Mediterranean and arid biomes.
But California is the land of a collective acceptance that "we can grow anything." In earlier times, botanists and entrepreneurs introduced countless non-native species to our landscape, and nurseries followed by providing sellable inventory, originally native to Asia, Eastern United States, northern Europe, and other locals where trees adapted to regular summer rains and humidity; two elements our dry climate does not provide. Consequently, trees from these other regions need supplemental water. Where no supplemental water exists, the summers can be brutal even in a good moisture laden year. Now look again at the landscape around you. Every neighborhood I have recently visited exhibits withering, desiccated trees that may not recover from this summer's drought. Dead ones, too, are seen in just about every neighborhood regardless of age.
Trees succumb when irrigation is shut off. Lawns die, lawn trees follow due to their shallow root systems. Street trees that never had irrigation, surrounded by concrete, cannot find water because any subsurface availability is gone. Especially vulnerable are new tree plantings, where they have not established themselves to adapt to their less desirable conditions. Do we give up all these trees? We should not swing the pendulum and cut our losses, because there are things we can do with minimal impact.
If you have trees that are struggling, you do not need to ramp up your irrigation and take on the added cost. People make a common mistake about trees, thinking they need irrigation scheduled several times a week or even once a week. In reality, most trees need a deep watering a couple times a month, some species even less. Saving your shower water? Take it to a struggling tree. Even using a soaker hose or sprinkle rosette set low for a half hour or so a few times over the summer could sustain many of the trees I see struggling now. Way back in the 70s when our family experience a drought, we saved our citrus trees with a slow dripping garden hose and a good layer of mulch, once every two or three weeks. Be creative! Boiling pasta? Save the water for a tree (let is cool first). For little effort and resources, urban trees can be saved, and I encourage you to look for these struggling trees and lend a little water.