The Oak Hotel

This time of year, my gar­den and lawn are car­pet­ed with leaves — not the orange and gold of autumn, but the dry, brown leaves of oaks. A lot of the Lan­dis Arbore­tum is cov­ered with the same brown rug. The fall­en oak leaves will be there for quite a while — they’re a lot more durable than most leaves. They form a dense mat, damp and sol­id, almost as tough as leather.

Paus­ing in the rak­ing, I observe that every sin­gle oak leaf has holes in it. Big holes, lit­tle holes, pin­pricks — all sorts of pat­terns of holes: the chew­ings and nib­blings and gnaw­ings of a mul­ti­tude of insects. 

They’re inter­est­ing pat­terns to look at, form­ing a sort of topo­graph­i­cal map of insect feed­ing habits. Some of the bugs take bites from the out­side rim and chew their way in. Oth­ers eat a round hole in the mid­dle of the leaf, neat as if cut with scis­sors. Some tiny insects, called leaf min­ers, tun­nel through the inner lay­ers of the leaf, eat­ing as they go. Tiny insects with the creepy name of ​“leaf skele­toniz­ers” eat only the soft­est tis­sue between the oak’s stur­dy veins, leav­ing a net­work of ​“bones.”

As much as I love oak trees, I’m not sad to see all these chew­ings. A huge infes­ta­tion of insects would be a dis­as­ter, but healthy oaks can with­stand a cer­tain amount of insect nib­bling. An oak can poten­tial­ly be food for hun­dreds of species of insects, there­by mak­ing it an arbo­re­al restau­rant for bugs. And for bug-eat­ing birds.

This is an intrigu­ing fact to con­sid­er, espe­cial­ly when you’re shop­ping for a species of tree to plant in your back yard. A non-native species like Nor­way maple, Siber­ian elm, or Chi­nese gingko isn’t food for our local insects, and so will have leaves nice and neat, with few­er holes — but the bugs and there­fore the birds go hungry.

It requires a rev­o­lu­tion­ary gar­den­er to wel­come munch­ing cater­pil­lars, leaf min­ers, and bee­tles into the gar­den and the for­est. It’s hard to turn your head and look away from holes in the very leaves you’ve so care­ful­ly nur­tured. But that’s the way nature works. Want to see but­ter­flies? You must wel­come cater­pil­lars. Want to see war­blers? Allow the insects they feed on to share your turf.

Oaks, per­haps more than any oth­er trees, pro­vide a huge amount of nutri­tion to the ecosys­tem of the for­est or the back yard. Not just the acorns, which are high-qual­i­ty nutri­tion for dozens of species of wildlife. Every oak leaf is a poten­tial feast for the insects of sum­mer and fall, and so oak leaves offer the promise of a feast for the birds of spring.