If You Can Plant Only One Thing, Make It an Oak

Dec 13, 2021

Foliage of a white oak *(Quercus alba)* in Rock Creek Park, Washington, DC. Credit: Katja Schulz

Full disclosure: I’m married to an Oakes (Quercus abnerus), so I may have a conflict of interest on this subject. But I hope you’ll give me the benefit of the doubt.

Things I Knew Before

Until recently, the list of things I knew about oaks -- the trees, that is -- was short. I present it to you here.

Oak Wood Is Heavy

One day, Abner and I were strolling in Manhattan and chanced upon a vendor selling Mission-style oak furniture on a street corner. It so happened that Abner needed a desk, so we bought one on the spot. It must have been cheap because we were both students with negative income. We apparently also had limited common sense, because it wasn’t until we owned the desk that we considered how we would actually transport it back to the apartment. We ended up carrying it. By hand. In the rain. The full 20 blocks. This was 30 years ago. My forearms are still sore. Take my word for it, oak furniture’s heavy.

Oaks Drop Acorns

Abner’s parents’ home in Connecticut backed up to woods and was encircled by several grand oak trees. Some years, they dropped so many acorns it became unbearable to walk in bare feet across the lawn. It was like traversing a field of toddler-strewn Legos. Excruciating.

Also, my father-in-law, known as “Poppy” to his grandchildren but not known for being crafts-y, made these adorable pendants for our son when he was little:

That was pretty much the extent of my knowledge of the genera Quercus.

Some New Things I’ve Learned

Deciduous, slower-growing and shade tolerant trees that favor less-fertile soil -- all characteristics of oaks -- tend to have more densely packed cells in their wood than do their fast-growing and evergreen friends. Density correlates with hardness and heaviness. So compared to cedar, pine and sycamore, for example, oak is quite dense. Hence the surprising weight of Mission-style furniture purchased on street corners.

Acorns are of course the fruit of an oak tree. A single tree can drop 3 million acorns in a lifespan. Every now and then, all of the oaks in an area will synchronize to produce disproportionately huge quantities of acorns. It happened in 2019, when red oaks from Georgia to Massachusetts coordinated on a massive collective nut dump. No one knows for sure why they do this. I’d like to think it’s for the entertainment value. Like an arboreal surprise party. (C’mon, guys. Shhhhh! Everybody wait ‘til Ringo gives the signal!) The working theories of actual scientists revolve around outsmarting predators, improving pollination yields, and/or rationing energy. This phenomenon is called “masting” and it explains the periodic Legoland effect I experienced in CT.

Acorns are rich in proteins, carbohydrates, fats and minerals, making them a winter staple for squirrels, chipmunks, rabbits, black bears, possums, raccoons, mice, voles, and many bird species. Oaks and jays have in fact co-evolved. Jays have a hook at the end of their beaks dedicated to opening acorns and an expanded esophagus capable of carrying five acorns at a time. (Think about how big your esophagus is and what it might feel like to cradle five acorns there. Now think about the size of a blue jay’s esophagus. Ow, right?) In return for the nutritious food, each jay inadvertently plants thousands of seedlings each year when it forgets where it buried some of its acorn stash.

More importantly, oaks are considered “keystone” native species. A keystone helps define an entire ecosystem. If it’s removed, it dramatically impacts the abundance and diversity of other species in the system. As University of Delaware entomologist Doug Tallamy says,

“Oaks support more forms of life and more fascinating interactions than any other tree genus in North America.”

It’s not just mammals and birds getting food and habitat from oaks, but many reptiles and insects, too. As noted in previous posts, most song birds in North America are primarily insectivores, particularly during the nesting period. Even though jays can carry acorns in their gullets, nobody wants to swallow those things whole, particularly not baby chicks. Instead they rely on soft, squishy caterpillars. So the hospitality of oak trees to moths and butterflies is a huge boon to birds.

There is wide variation among plants in “insect productivity.” This is the degree to which they provide habitat or food to bugs, which in turn supports other animal populations. Invasive plants tend to be the least productive; other non-natives are also weak on this score. For example, a crepe myrtle, which is native to eastern Asia, supports three species of moths and butterflies, while a native oak can support more than 500.

Lest you crepe myrtle-harborers out there think I’m judging you, know that in the 25+ years we’ve lived on our small plot of land, I’ve managed to plant 6 (six!) crepe myrtles. In that same period, I’ve planted 0 (zero!) oaks. We’re in this together, ok?

Even among native plants, there are significant differences in productivity. Again from Tallamy:

“If you have an oak or black cherry or black willow in your yard, there will be enough insect food for at least a few birds to reproduce. But a yard without keystone plants will fall far short of the insect abundance necessary to sustain viable food webs, even if dozens of native plant genera are present.”

A glorious overcup oak (Quercus lyrata) at US Botanic Garden, Washington, DC

If You Already Have an Oak, Give It a Hug

Oaks are not only keystone species, but -- like other sizable trees -- they create their own microclimates. They buffer harsh winds. They produce shade that supports sun-averse plants and deters invasive species. In hot summer weather, it can feel 15 degrees cooler beneath a mature oak and -- get this -- a stand of them can create its own breeze. Oaks tend to hold onto their leaves longer than other deciduous trees, sometimes straight through the winter, which means they can trap more snow, increasing soil moisture at their base relative to surrounding areas.

Because of their expansive leaf surface areas and root systems, oaks intercept a lot of rain water before it can turn into runoff, helping to mitigate flooding. And because of their cell density (see above) and long lifespans, they’re awesome at sequestering atmospheric carbon dioxide. In other words, they provide invaluable ecosystem services to us humans.

Is there a special oak (or Oakes!) in your life? If so, tell us about it in the comments. Let’s hear some Quercus shout-outs.

The Bees' Knees

Discussion about this post