Fall 2025
The Mighty Oak
By Jackie Howland
When I was a little girl, I came across a poem that really inspired me. I couldn’t remember the whole thing but putting the line I recalled into a search engine quickly brought it up. I also learned the author is anonymous. Here it is:
Of course, I mostly remembered it because it made me laugh, but there’s also a serious side to the message. Just think. Something that can grow up to 100 feet tall and produce hundreds of pounds of wood starts from an acorn even a very small child can easily hold in the palm of their hand.
But wait – there’s more! Far more, actually. Obviously, as all trees do, oaks store carbon and emit oxygen, something even more critical now than ever. And you may be thinking about the birds and squirrels who hang out in oaks, but that’s just the tip of the iceberg. It’s estimated that oak forests can support up to 1,000 species of animals and insects. That’s a lot to do for even the biggest oak, and it’s why they’re a keystone species in our ecosystem, meaning they are disproportionally important when compared to other plants. Let’s look at the ways they contribute to our natural community as well as our own well-being.
We’ll start with those acorns. Most people probably associate acorns with squirrels or chipmunks and maybe scrub jays. But did you know they’re also consumed by possums, bears, deer, and even moose? Acorns are high in fat and carbohydrates and have some protein as well, so they’re an excellent way to consume calories. And, of course, they can be stored or cached over winter, which can help certain animals survive when little or no other food is available. Humans have used them as a food source as well, but the high tannic acid content makes them unpalatable to many of us. Still the acorn was and continues to be an important food source for some Indigenous tribes in the US and feasts honoring their traditions may include meal or flour made from acorns.
They must first boil the shelled and cracked or ground acorns to wash out the tannins and reduce the bitterness. The whole process of gathering the acorns, shelling them, cracking or grinding them, and then leaching all the tannins out might seem quite labor intensive to us for something that’s still fairly bitter. However, about the same amount of labor is necessary to pick, dry, roast and grind coffee beans and coffee has very little nutritional value. It’s all about what we value and yes, I do value the caffeine!
California is home to many types of oaks, which are adapted to specific conditions such as thin, rocky soil or deeper top soil. Note that different species of oak produce different sizes and shapes of acorns and their caps. These were collected locally.
As with other plants that produce nuts, seeds, or fruits, oaks have evolved to reproduce in a way that helps ensure their offspring get spread around. The acorn may not fall far from the tree, but animals will carry them away, often caching them by burying them. Acorns that aren’t retrieved are likely to grow in the spring, as those of us with potted plants or vegetable gardens may discover to our dismay. Soft moist soil is usually preferred over the hard dry stuff, both by the squirrels and the acorns. It’s a win-win situation for them.
The relationship between oaks and other species extends to other benefits for the animals if not always for the oaks. Many birds nest in oak branches and then feed their babies the caterpillars eating the oak leaves. Some creatures live or nest in cavities in the oaks’ trunks – owls, woodpeckers, wood ducks. Other animals dig burrows under the large roots. Rabbits, wood chucks, or foxes are some examples. Rotting oak wood provides food and/or homes for things such as grubs and salamanders. You can find all kinds of wildlife in an oak forest.
However, the largest group of animals that depend on oaks are bugs. Smaller insects deposit their eggs in leaves or create oak galls. The bark is a place to hide for beetles, including lady bugs. Beetles may feed on the wood. But stir up the leaf litter around an oak and you’ll also stir up bug city! Earthworms, pill bugs, earwigs, centipedes, and more all love hiding in and/or feeding on the decaying leaves. These creatures then attract larger animals that feed on them.
Let’s not forget the unseen stuff, though. Rotting leaves and the waste from creatures that feed on them in turn feeds the microbial life that’s so essential to our ecosystem. We’re just beginning to truly understand how all this works, but it’s clear that nature is the expert at recycling matter. In the case of the oak, the tree pulls water and nutrients deep from the soil, combines these with the energy formed by photosynthesis, and then sheds it all in the form of leaves and wood. Other creatures in turn recycle all this so that it’s available to other plants. Oaks also return water to the ecosystem in the form of evapotranspiration through their leaves. That helps cool the area around the oaks in summer and is why oak and other kinds of forests actually help modify climate.
This isn’t so difficult to understand if you consider deserts, where plants tend to be small, sparse and more spread out. Temperatures soar during the day in the desert, but then drop way down at night. There’s little to prevent heat gain or loss and the same holds true for moisture. We can’t change a desert into a forest just by planting trees, though, because natural deserts are a function of climate zones and geographical features. Unfortunately, humans have contributed to increasing deserts by the destruction of grasslands and forests, mostly through overgrazing by sheep and goats. Clearcutting large areas of forest lands doesn’t help either.
It’s super important to maintain forests and woodlands as well as individual trees for our own sake as well as other life. Oaks can be a wonderful addition to a property if they’re in the right place and taken care of properly. Oaks native to California are adapted to our Mediterranean-type climate, which means they find their own water. Trying to have a lawn around an oak is just asking for trouble. The daily watering of the lawn can lead to oak root fungus and other oak pathogens that can kill oaks. Older oaks may also drop very large limbs in the summer or fall, endangering people and property. All native California oaks need to have a dry zone all the way out to their drip lines and preferably be somewhere where a sudden limb drop won’t damage people, animals, buildings or vehicles.
If all these factors are in place, an oak tree can be a wonderful neighbor, as this one is to Gateway Science Museum. You can see it in the back garden above the water feature. And right now it’s got lots of nuts like me!