Oak Tassels – what are those worms on my driveway?

Newly emerging leaves on a red oak in the spring with male flowers

This spring season has brought with it an abundance of oak flowers or “tassels.” I have noticed it on all of the oak species: live oak, post oak, blackjack oak, shumard (red) oak, etc. They all have a bumper crop of male flowers this year.

Oaks are monecieuos, which means that they have both male and female flowers on the same tree. The male flowers are called “catkins” and hang down allowing the wind to pick up the pollen that they produce and send it to any receptive female flowers on the same tree or ones close by. The pollen this year has been very heavy, coating cars and everything else outside that is exposed to the wind-blown pollen with a yellow green film.

For allergy sufferers that are sensitive to oak pollen, the flowering should be over soon and the pollen  in the air should be decreasing over the coming weeks. 

I don’t know if the abundant male flowering will translate into an abundant acorn crop this fall. The female flowers are much more inconspicuous and I haven’t had time to get into some trees to see if there is a corresponding abundance of female flowers.

At any rate, the “worms” on your driveway are male oak flowers that have done their job of releasing pollen and are now dropping from the trees.

Scott Geer

Scott Geer

Scott Geer has a master's degree in forestry from Stephen F. Austin State University and is an ISA Board Certified Master Arborist.® He is also a graduate of the American Society of Consulting Arborists Academy.