New Category: Old Wives’ Tales

An alert reader had two observations from the world around him. He was in a new area and noticed that the horticulturists painted the trunks of trees white and they filled the cavities of tree trunks with cement. Both of these, I think, are in the category of old wives’ tales. Both are based on partial truths and a lot of tradition. So with apologies to the old wives, let’s examine these practices.

First, the white painting on tree trunks. It is my belief that this got started way back in Europe with lime sulfur. Lime sulfur is a slurry of stuff that coats insect eggs and kills them pretty well. If you have a tree in the dormant condition, you spray this noxious smelling gunk on them to kill scale and insect eggs. It works partially so it has become wildly popular again for non-chemical pesticide spraying. I would use it myself for scale as it dries the shell of the insect out without hurting the tree. The lime makes the tree kind of white-ish. The lighter color also has the effect of reflecting winter sun. Sometimes in the winter, the sun comes out on a cold day and shines warmly on the trunks of frozen trees. It is possible that the trunk warms up, and thaws. Later that night when the warm sun sets, the trunks very rapidly cool down. Since the outer layers of the trunk freeze faster than the center, the trunk can contract on the outside and crack, leaving a nasty open split. Painting the trunk white with lime reflects the sun, avoids the warming and the subsequent cracking. The weather conditions that cause this are very particular, and in practical situations, very rare. But rare or not, this CAN happen and lime can help with this. The lime spray has been used by orchardists for hundreds of years for weak insect control and frost crack prevention. In my opinion, lime is not very effective for either purpose but I do admit that it can help a little bit. In any case, lime sulfur would not generally be harmful so at worst it is a waste of your time, and at best it may be beneficial. Is it worth my time or trouble? No. Is it steeped in folklore of miraculous insect prevention and frost protection? Yes. You decide on whether to paint your trunks or not.

Now that is the original recipe for the whitewash for tree trunks. Without knowing exactly why, people have it in their heads that trunks need to be painted white. So then they use latex paint. Lime sulfur may be a harmless horticultural practice but latex paint is not. Latex paint can be suffocating to the tree cells underneath it. It can cause the cells to necrose and die. This can cause very bad dead areas in the protective “skin” on the tree and resulting rotten areas. So, tree trunks painted white? Not necessary and usually done by people who have a lot of time on their hands with nothing better to do.

The next old wives’ tale is cement in the cavities. First of all, if your tree trunk is so rotten that it has a big cavity that a squirrel or bear might live in and you want to fill it with cement, you need to get a new tree. Filling trees is an old-time tree technique that is avoided nowadays because proper trimming and tree removal when trees are unsafe are better strategies. Can you imagine the lawsuits that would be filed in this country if you left a street tree standing that had a big hole in it and then a storm knocked it down on someone’s house or car? No, a hollow tree is a weak tree and a tree filled with cement may be sturdier but it is brittle. Wind can knock over those kinds of trees in a big storm. I would not do it. Old wives’ tale #2.

Please send me your other dubious horticultural practices; I like this new category!

P.S. Old wives’ tale #3 was just discussed a couple of days ago. Ants are NOT necessary for peony buds to open. They just like eating the sugar.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: