Within a gardener’s life, a single tree can transform the garden.
A good example is the red oak (Quercus rubra) that grows at the edge of Marjorie’s Garden. Now 40 feet high and half as broad through its longest branches, I have watched it more than triple its size since first meeting it 12 years ago. For a dozen springs I’ve watched it unfurl new leaves of russet red, then lift these same leaves turned yellow-green to the sun, and I have watched those leaves through summer green and back to russet red in October, then to dark amber in November morning sunlight, finally to tattered brown on the frosted ground, torn away by December winds.
Our garden oak began flowering in 2004 when it was still a slick-barked young tree, and each spring since then its golden staminate catkins have released their pollen on the wind to mix with pollen from other oaks in the area. And so for the past nine years there have been acorns on the ground around our garden oak.
This oak has transformed the garden. A nearby perennial bed, once considered suitable only for full-sun plants, gets shadier each year. We have encouraged the transformation, removing spruce and fir that crowded the oak. Everything that can be done to enrich the future of this oak, we do.
Our red oak is a playground for scampering red squirrels and chipmunks, a feeding ground for songbirds. Writing by a window that looks out on the tree, I watch blue jays hopping among the branches, chickadees darting in and out of the canopy as they feed on insect eggs and larvae, nuthatches creeping upside-down on the trunk in search of bugs, black-and-white warblers in the topmost branches nipping at – what? – on the surfaces of leaves.
Late in a spring afternoon, thousands of crepuscular insects swarm in the canopy of our red oak while caterpillars crawl over its new leaves. Many of the flying adults are tiny moths laying eggs; their caterpillars are called leafminers, one of the many types of leaf-eaters. Some of the insects are adults or larvae of predator species that will help control plant-eating insects throughout the garden.
In spite of the birds and predacious insects, by mid-summer most of the oak’s leaves are riddled with holes, ragged with chewing, punctuated with galls. But the oak always has leaves to spare. Acorns grow to full size, then disappear.
Who eats the acorns? Certainly the red squirrels and chipmunks, but possibly the wild turkeys, raccoons, deer, black bear, and mice that share the garden with us, creatures that visit the garden at night or in our absence during the day, leaving only tracks. All we know for sure is that it takes only a week or two and the acorns are gone.
In late October, after the sugar maples have shed their technicolor leaves, red oaks like this one will paint the hills in rich earthy tones of yellow-brown and russet red. And then one November night a strong wind will break the already weakened connection between petiole and twig and most of the rain-soaked leaves will fall to earth. Winter winds will drive snow against the trunk of our oak, calmer snows will trace its strong horizontal limbs. Crows will greet frigid sunrises from the highest branch.
Come spring, again we watch young red squirrels chasing one another around the red oak’s bole and through its branches. No doubt, it was a squirrel that started it all.
Douglas Tallamy, in his popular book “Bringing Nature Home: How Native Plants Sustain Wildlife in our Gardens” (2007, Timber Press), tells us that oaks top the list in terms of supporting lepidopteran larvae; over 500 species of butterflies and moths depend on the different species of oaks for food. Turn over an oak leaf, find a caterpillar, and you understand what bird food looks like.
In addition to the larvae of moths and butterflies, including hairstreak butterflies and skippers, red oaks support gall wasps, leaf beetles, acorn weevils, aphids, leafhoppers, treehoppers, and plant bugs. This diversity of herbivores attracted to the red oak will in turn bring a diversity of predatory insects and insect-eating birds into the garden to help control herbivores found on vegetable plants, small fruits, and ornamentals.
During nesting season, when songbird requirements for insect protein reach a peak, I have noticed goldfinches and purple finches leave the porch sunflower feeders to feed on insects in the oak. I also see them in the vegetable garden where, along with warblers and hummingbirds, they work to keep herbivore populations at a minimum.
As an organic gardener who eschews pesticides of all kinds, I give the red oak much of the credit for any successes. Anything that can be done to ensure its future, we do.