Shady Business: Trees and Drought

One of the perks of having trees nearby is that social-distancing rules don’t apply – you can hug as many as you like without risk of contracting Covid-19. Another benefit, of course, is shade.

When the heat’s on and you need to lie low for a while, it’s great if some of your friends are shady characters. Especially if they’re tall, mature types with solid builds. Yeah, trees are cool.

When the thermometer spikes, any shade is welcome. If you’re lucky enough to have large trees where you live, not only can you get a break from the sun, but the air temperature will be cooler – as much as ten degrees – as compared to out in the open. It’s an awesome, natural, and free kind of air conditioning.

Speaking of which, if you use an air conditioner, having shade trees on the south and west sides of your home will reduce your cooling costs by a minimum of 30%, and possibly as much as 50%. It’s like getting a refund on part of your electric bill. Deciduous trees are ideal because they shield you in summer but allow sunlight through in winter when you want it.

On those blistering summer days when you think it’s too hot to work outside, you’re not alone – trees share your outlook. Photosynthesis, that amazing process which turns carbon dioxide and sunlight into sugar (thereby keeping the trees alive) and oxygen (thereby helping keep us alive), does not work well above 85 degrees. All that solar energy going to waste! Incidentally, leaves can get too hot in full sun even when the air temperature is moderate, much like the way an asphalt parking lot gets scorching in the sun.

This is why a tree’s inner canopy is essential. Far from being ill-fated residents of an undesirable neighborhood, leaves that are shaded, and thus cooled, by the upper canopy are key players in a tree’s survival, as they’re the only ones on the job when it’s too hot for their upstairs neighbors to work. So it’s best not to get overly enthusiastic with pruning. Trees don’t want their inner canopy “cleaned out” to any great extent.

Hopefully you’re drinking plenty of water in the summer heat. It might surprise you that trees can run short of water, especially in hot, dry seasons like 2016 and 2018. While we tend to think tree roots dive deep in search of a cool drink, 90% of tree roots are in the top 10 inches of soil, and 98% are in the top 18 inches.

A brown, dead-looking lawn will recover from drought in a matter of weeks, because grass has a mechanism to become dormant without suffering harm. Trees, however, take several years to fully recover from an extended summer dry spell. Drought stress weakens a tree, making it more vulnerable to diseases and insects.

While many shady characters don’t take well to a soaking, your tree will appreciate a thorough weekly drench. Forget the lawn – it can fend for itself. Please remember your trees, and water them thoroughly if it hasn’t rained in more than a week.

I wish you all a healthy, well-hydrated summer, and lots of hugs with your shady associates.

Photo of Sugar Maple courtesy Wikimedia user Bruce Marlin.