It’s Arbor Day! the one day a year we’re all supposed to feel guilty about not having planted a tree yet. But before you grab just any sapling from the garden center and call it a day, we need to talk about the oak tree. Because planting an oak isn’t just gardening. It’s an act of ecological heroism, basically wearing a cape, except the cape is shade, and it lasts three hundred years.

Here’s the thing most people don’t know: a single oak tree can support over 500 species of caterpillars and other moth and butterfly larvae. Five hundred. That’s not a tree that’s an all-inclusive resort for insects, and every guest is doing important work. Compare that to a Bradford pear (a tragically popular landscaping choice), which supports a whopping zero to five species. Planting a Bradford pear is essentially putting up a “No Vacancy” sign for wildlife, while the oak rolls out the red carpet.

“But why caterpillars?” you ask, reasonably. Excellent question. It turns out baby songbirds are extremely picky eaters and not in an annoying toddler way, but in a biological survival way. Soft, juicy caterpillars are the perfect baby bird food: high in protein, easy to digest, and conveniently wriggly. Research by entomologist Doug Tallamy found that a pair of Carolina chickadees needs to bring between 6,000 and 9,000 caterpillars to the nest just to raise a single clutch of chicks to fledging. That is an absolutely staggering number of caterpillars – a full-time job, a second job, or even a third job with no benefits.

And here’s where the oak swoops in like a leafy superhero. Without trees like oaks nearby ones that actually host caterpillars parent birds simply cannot find enough food. Neighborhoods full of exotic ornamental plants might look lovely to us, but to a chickadee parent desperately hunting for the 4,372nd caterpillar of the day, they’re basically a desert. Birds in these areas often fail to successfully raise their chicks. The forests go quiet. And nobody wants that.

“The oak is, in many ways, the most generous tree in North America feeding insects that feed birds that fill our mornings with song. It’s a whole ecosystem hiding in plain sight, wearing a disguise of handsome bark and autumn leaves.”

So this Arbor Day, skip the trendy ornamentals. Plant an oak. Yes, it grows slowly, and you might not sit in its full shade for a decade. However, you’ll be planting something that will outlive you, outlive your children, and possibly outlive your grandchildren’s children all while quietly running the most efficient wildlife bed-and-breakfast imaginable. Hundreds of species of caterpillars, thousands of birds fed, and one very satisfied squirrel who will absolutely bury acorns all over your lawn without a thank-you note.

Plant an oak. The birds are counting on you. Literally counting up to 9,000.