What is it about Red Oaks?

Every autumn I fall in love with ‘fire on the mountain’…This year the maple show was relatively brief, with scarlet leaves dropping early, although in mid October some larger maples still have bittersweet gold and sunset orange leaves. Drought is becoming more and more of a threat in our neck of the woods overall, and this year almost all the trees deciduous or conifer are suffering. Insect damage is pervasive and I have seen more diseased trees this year than ever before.

Which brings me to red oaks. I notice on my daily walks or while climbing nearby mountains that my eye is drawn to the graceful green oaks overhead, or to the brilliant crimson of smaller oaks that abound in the understory. Some oak leaves, of course, are already brown but many still vibrate with astonishing colors in mid October. Along with the moose 

 Maple, these smaller trees are striking in appearance, many with (apparent?) oversized leaves. A young friend of mine postulates that these large leaves help the seedlings photosynthesize more effectively, a perspective that I suspect has merit. 

When I first came to this land I noted the absence of oaks with dismay. Upwards of a hundred species of animals/birds need acorns to sustain them through the winter. To redress the apparent imbalance, on my woodland meanders, I started picking up acorns from the red oaks that I then planted in various places on this property. I did this year after year without any tangible results. And then about fifteen years ago I began to notice young oaks sprouting along my paths or around the house. By then I also had a healthy population of Blue jays as well as squirrels so I wondered who had done the planting. Blue jays select undamaged nuts to bury; I don’t know about squirrels. Amazingly according to the research that has been done only ten percent of the jays cached acorns are NOT viable seeds. Blue jays also spread buried seeds over a large area; as a result a number of species of oak trees have become dependent on these birds for acorn dispersal. So the next time you complain that there are too many jays at your feeder (as I certainly have) remember to thank them for planting new trees! 

The other fascinating fact I learned just recently is that oaks like to grow with white pines. There is a reciprocal relationship between the two trees on a mycelial level. When I discovered this piece of information I realized that the oaks around here didn’t begin appearing until the pines began to grow up through the field… coincidence?  And what do the blue jays know about this relational finding?

Last spring I selected one healthy red oak acorn to germinate in the house for fun. Sure enough it wasn’t long before a tiny seedling emerged. I let the seedling grow most of the summer in a pot to develop a good root system and recently planted it in a sunny spot. By then the tiny tree had lost all but one bright red and green leaf that pointed skyward like a sword. Like so many young oak trees insects had attacked the other leaves leaving gauzy translucent webs; some curled up and dropped.

Have you ever found yourself struggling for traction on a steep slope while on a fall walk in a hardwood stand? The cause of that slipperiness might have been freshly fallen northern oak leaves, which have waxy surfaces. Both acorns and the leaves are tied to the oak’s evolutionary strategy.

Red oaks evolved in concert with the now extinct Passenger Pigeon. It is estimated that 2 to 5 billion of these plump birds once inhabited the eastern forests. Their primary fall food was red oak acorns, and they would descend on forests in the midst of good mast years in such abundance that they would break off oak branches, creating ‘kindling’ on the forest floor. It’s important to note that the waxy oak leaves are fire prone once dry. This adaptation, combined with the life history of the Passenger Pigeon, helped create conditions for surface fires that oaks can often resist, but that may kill competing species.

Part 2

You can spot red oaks in spring, when beautiful pink leaves covered in silky down emerge from the trees’ buds. Keep an eye out for them as you explore the woods. We have two species of oaks that are common in this area. Red and white oaks have distinctly different leaves and acorns. Red oak’s leaves have pointed tips and are five to ten inches long (even on seedlings) and have rounded acorns. White oaks have rounded lobes and elongated acorns. In summer, both oaks have leaves that are a dark green, and they turn a rich red or brown in fall.

Northern red oak’s distinct bark makes the tree easy to identify even without leaves. Irregular reddish stripes lie in between rougher ridges. A few other oaks have bark with this kind of appearance in the upper branches, but the northern red oak is the only one with striping all the way down the trunk, except in trees of very large diameter when the bark becomes rougher at the base. Red oaks often hybridize with black and scarlet oaks.

If allowed to live long enough in forests, these trees grow straight and tall to a height of about 100 feet, though exceptional trees will reach 140 feet. Their trunks reach up to 40 inches in diameter. When they grow in the open, red oaks don’t get as tall but they can develop stouter trunks, up to six feet in diameter. Trees may live up to 400 years or more.

 Northern red oaks grow rapidly and are tolerant of a variety of soils and site conditions, though they prefer well-drained lower areas. Most species of oaks including red oaks don’t begin to produce acorns until they are thirty years old – the time when many of these trees are already being harvested for timber. Peak acorn bearing trees are between 50 to 80 years old, and certain trees produce more acorns than others, a phenomenon that can be baffling – highlighting how little we know. On a good mast year adult red oaks produce many acorns.

Red-oak acorns take two years to mature, are exceptionally high in fat, and don’t sprout until the following spring, even when buried. As a result, the acorns keep. Birds and animals rely primarily on red-oak acorns for their winter stash. White-oak acorns mature in a single year, are sweeter than the reds, and sprout soon after falling, losing their nutrients rapidly so they are eaten by wildlife immediately. During years when fall mast is plentiful many acorn – eating species including jays, wild turkeys, grouse, mice, chipmunks, squirrels, raccoons, bears, and deer all seek out this high protein/high fat nut to help them survive the winter.

In spring look for the flowers that form on the trees. At the base of the tiny female flowers, the cells swell into a vase shaped ovary topped by a pistil ready to capture any wind blown pollen… after fertilization the ovary becomes the acorn, the petals the cap.

There are eight species of oak that occur in Maine – the confusing part is that some of these species hybridize with others.

Scientists have barely begun to unravel the many ecological repercussions of the oak forest’s wax-and-wane mast cycle. For that matter, they’re not entirely sure whythe nut crop varies as it does. Certainly weather and other environmental influences are a factor — a drought can sap trees of reproductive energy; a late spring frost can kill flowers. But weather doesn’t appear to be the main influence. Bumper-crop years aren’t always especially weather-blessed. Poor mast years occur even when conditions are ideal for acorn growth.

Many scientists now believe the mast cycle is an evolutionary adaptation; that over the eons oaks and other nut-bearing trees have developed an on-and-off mast cycle to ensure their reproductive survival. This theory makes sense to me. If oaks produced a consistently healthy crop of acorns every year, populations of nut-loving animals would rise to the point where all the acorns would be eaten no matter how numerous. None would remain to grow into mighty oaks and we would be overrun with squirrels and chipmunks even more than we are right now!

The theory around the mast cycle solves the problem. During moderate to poor years, wildlife suffers, seldom increasing and often decreasing in numbers. Then comes a good year, when the trees produce far more nuts than the animals can consume, and acorns are left to germinate and renew the forest.This fall it is especially easy to see the red oak seedlings. They seem to be popping up everywhere. The next time that you are in the woods look for the small oaks that still display  abundant colors, and hope that some will survive the rapacious timber harvest to become nut bearing oak tree adults…

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