80801thumbSevere summer weather is something that we think that we do not need to contend with. It only rarely gets as unbearably hot here as it does elsewhere, and when it does, it usually gets breezy by evening, and somewhat cooler overnight. Aridity, or the lack of humidity, is another advantage, at least for us. The plants in our gardens are affected by warm weather very differently than we are.

Plants will tolerate significantly more warmth than we will, but only in conjunction with humidity. In our climate, we get one or the other, but not often both. In fact, humid warmth is so rare here, that when it happens, it causes spontaneous limb failure in trees that are not accustomed to it. Spontaneous limb failure occurs as vascular activity accelerated by warmth increases foliar weight, but humidity inhibits evapotranspiration (evaporation of moisture from foliar surfaces) that would decrease the weight.

The aridity and breezes that make warmth more comfortable for us accelerate evapotranspiration, which increases the need for moisture. Plants that lack adequate moisture wilt, and the foliage of some can get dehydrated or scorched. Wilted plants recover if watered soon enough. Dehydrated foliage is crispy and can not recover. Severe dehydration kills buds, stems and entire plants.

Scorch is quite different from dehydration. It happens as overly exposed foliage literally gets cooked by sunlight. It is similar to sun scald on formerly shaded bark that gets cooked by sunlight after being exposed by pruning or other means of removal of adjacent vegetation. Scorch is more likely on inner foliage that had been recently exposed by pruning, or foliage near reflective surfaces.

Foliage can not recover from scorch. Damage is permanent, and should not even be pruned away. Just like foliage damaged by frost, outer foliage damaged by scorch shelters the inner foliage. Removal of damaged foliage exposes foliage behind it to subsequent damage. Besides, scorch typically damages only parts of individual leaves, so that undamaged parts continue to function.

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15 thoughts on “Summer Weather Can Scorch Foliage

  1. unfortunately, we see this on occasion ( more over the last two years). We have a Rodgersia in one of the display gardens that is getting too much sun after the trees that were shading it came down, as well as not getting the typical rain we depend on. One would be tempted to trim off the damaged leaves, in this case, a very few, but then risk the ones behind it getting scorched as well. Today, however, we are getting a decent dose of rain and it is also expected through the week. Hurray!

    Liked by 1 person

      1. I’m in the Houston area and we are hot and humid. Dallas, our rival city, is dry and they always say their don’t have our awful humidity so it is not as bad there. But hot is hot especially as we have both been over 100 degrees.

        Liked by 1 person

    1. Thank you. I am pleased that you found it to be informative. Ironically, the damage here occurred because the weather had been so mild, and then got warm suddenly. Even then, it was not too unnaturally hot for our climate. All this happened while everyone else was getting that nastily hot weather.

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