By ETHAN TAPPER
On my property in Bolton, I am engaged in a long-term management regime to regenerate and encourage northern red oak (Quercus rubra; henceforth called “red oak”). My thin-soiled, south-facing land provides what a forester or logger might call “oak ground,” an area well-suited to the growth of this species. About 20 years ago, loggers removed most of the red oaks on my land, leaving only massive stumps and tops, so now I’m forced to consider how to manage my remaining red oaks and regenerate more. I’ve become so red oak-obsessed that I often refer to them wistfully as “the ultimate tree.”
Northern red oak behaves differently throughout its range, so let’s talk about it within the context of Vermont. Here, red oak is our most common oak species; white oak (Quercus alba) is scattered throughout river valleys and warm sites, bur oak (Quercus macrocarpa) and swamp white oak (Quercus bicolor) are found in clayplain forests, and there are a couple of other oddball oaks around, but these species are comparatively uncommon; generally, when people in Vermont talk about oak, they mean red oak. Red oak is somewhat common in warmer portions of the state (southern and western Vermont) and increasingly uncommon as you head into the Northeast Kingdom.
Here, red oak is generally most competitive on south-facing slopes and sites with thin or droughty soil. Driving on I-89 along the Winooski River in the late fall, once the leaves of most species of trees have dropped, the rusty foliage of red oaks blankets south-facing slopes. These warm, dry sites often feature red oak as a dominant tree species along with American beech, red maple and eastern hemlock. Red oak can also thrive on lower slopes in the Champlain Valley, co-existing with species like sugar maple and white ash, but is generally less competitive as soils become wetter, cooler and more enriched.
Red oak acorns are an important source of food for deer, black bear, squirrels, turkeys and other wildlife species. These energy-packed nuts help animals build up their reserves going into winter, and good “acorn years” (also called “mast years”) are linked to population increases in many different wildlife species. Red oak is also a valuable resource for humans, providing high-quality firewood and beautiful lumber.
Regenerating red oak is extremely challenging. The easiest method is to harness red oak’s ability to sprout prolifically from freshly cut stumps; many of our red oaks were established this way, and so are actually much older than they seem. Regenerating from seed is more difficult, as acorns are subject to intense predation. Red oak acorns take two years to develop, and only about 50 percent of them reach the forest floor as viable nuts. Once they fall, up to 98 percent of them are eaten or destroyed. Oak trees limit the populations of acorn predators by coordinating “mast years” across regions, producing a glut of seed every 2-3 years with few produced in the interim. In the heavy mast year of 2017 I buried thousands of acorns on my land, covering those lying on the ground with an 1-2 inches of soil. “Planting” acorns in this way can lower predation rates to about 50 percent.
For the lucky ones that sprout, energy-packed acorns enable young oaks to establish deep taproots. Red oak seedings are extremely shade-tolerant, able to remain in the forest’s understory with little to no direct sunlight for as long as 20 years, waiting for an opening in the canopy. During that time, they are vulnerable to deer browsing (they are one of deer’s favorites), and to being outcompeted by beech root-sprouts and invasive exotic plants. Their taproot helps them re-sprout if they are browsed, damaged or burned, but if they are repeatedly damaged they will eventually die.
Foresters and landowners, like me, who want to grow red oak must be patient and persistent. Taking a long view, working hard to recruit new red oak seedlings at every turn and timing forest management to occur on mast years is key. Steps must also be taken to protect vulnerable seedlings, limit deer browse, control invasive species and possibly control beech sprouts.
While red oak is at times challenging to manage, I still think of it as “the ultimate tree.” Its value for wildlife, its role in unique natural communities and its beautiful wood make it worth the trouble.
Ethan Tapper is the Chittenden County forester. He can be reached at firstname.lastname@example.org, 585-9099 or at his office at 111 West St., Essex Jct.