Why do orchard trees have a white ring around the bottom?

Many of our trips involve driving through the Central Valley of Northern California which is covered in orchards, particularly olive and almond. Not always, but frequently the lower part of the trunk of orchard trees are painted white.  If it were just one or two orchards, we might chalk it up to somebody trying a new-fangled idea, somebody not willing to let go of an old-fangled idea or a farmer who’s either weird or WAY too into conspiracy theories.  Personally, I really like the latter theory.  Unfortunately, there are far too many orchards that have implemented this practice to go with the secret government conspiracy theory.  So of course, my friend Google and I did some searching.

 
Almond orchard with white washed trunksIt turns out that this is an age-old practice to help protect young trees from all sorts of unsavory things like borers, the tree equivalent of sunburn (called sunscald) and the introduction of diseases, insects and the like from cracked bark.
 
While there are many opinions about what type of paint to use latex paint (either indoor or outdoor) diluted by half to 4x is sufficient for the task.  How often should it be applied you ask?  I’m glad you asked :-).  It’s applied once per year.
 
So there you have it – why orchard and tree farmers paint a white ring around the lower trunk of their trees. 😊