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Even those among us who are decidedly indoor enthusiasts would be hard pressed not to have noticed the large volume of leaves on the ground at this time of year. Next time you find yourself kicking around in a pile of these leaves, you ought to stoop over and see if you can pick out a handful of oak leaves.

They are lobed, symmetrical, and you may find some pebble-sized, furry growths on some of them. What you have found are likely oak galls; they are formed by a parasitic wasp which has had an exceptionally good year.

Before you throw down your handful of leaves screaming in fear, you should know that humans have nothing to fear from these little wasps. In fact, the oak trees themselves have little to worry about.

Although the gall may interrupt some photosynthesis, and they are perhaps mildly unsightly, these leafy galls won’t greatly affect the health of the tree.

The most beautiful part of these furry oddities is the way in which they are formed. The parasitic wasps will burrow into the buds of the tree and secrete a chemical that signals to the surrounding cells to duplicate. The duplication of cells causes this abnormal growth where the wasps can lay their eggs to assist in their survival during the winter.

If you are interested in learning more about this process you can read about it in Ron Meader’s article for the MinnPost entitled “An investigation into those odd, fuzzy, puff balls… ”

It would definitely be logical to ask how these organisms evolved to secrete such chemicals, or why there are so many galls this year. The truth is that we know very little about these organisms and how they came to be.

We can speculate that the weather was favorable this year, but no one knows the truth. Perhaps someday you will give us the story of how these furry little oddities came to be.