Nutfall: Acorn crops are variable

Doug NC/Flickr

Doug NC/Flickr

It won’t be long before everyone’s dealing with the season’s bounty of fallen leaves. For many households, though, the leaves are less of an issue than the annual hailstorm of acorns.

In areas where oaks are prevalent, acorn fall can be a very big deal. It’s a boon for squirrels (and bears) but can be a major nuisance when the nuts, slippery under foot, cover every square inch of the lawn, deck and driveway.

Some years are banner years for acorns or mast, as the hard nut crop is sometime known among wildlife-watchers. That doesn’t mean the same will hold true this year since the acorn production varies from year to year, species to species and region to region.

The two commonest oak species in New Jersey are the white oak and the red, the latter being our state tree. White oaks will bear heavily in years when red oaks have few acorns - and vice versa. So no one who has both types can reliably hope to be spared an acorn inundation.

The acorn cycles of these trees are very different. Species in the white oak family produce mature acorns in just three months while those in the red oak group take 15 months, two whole growing seasons, to ripen a crop.

What makes predictions about the crop a little more complicated are factors related to age, tree species and weather. Even tree scientists don’t fully understand the process, although a couple of things are generally true.

Younger trees under 20 years of age often have few acorns while they devote their resources to gaining size and girth. More venerable trees between 50 and 200 years old are acorn over-achievers. We also know that each oak species has a particularly heavy crop every two to 10 years. In a lean year, there may be none; in a fat year, there might be as many as 23,000 acorns per tree.

The heaviest bearing trees are those that have successfully dominated the woodland. Trees with crowns that have risen above their neighbors and enjoy abundant sunlight are going to bear heavier crops than those that are shaded. This explains why that specimen oak in the middle of your lawn is a very happy acorn machine.

Weather is important, too – not during autumn, but in the spring when the oak trees flower and the leaves are first emerging. Like most trees, oaks are wind pollinated and a major source of the pollen that produces symptoms of spring "hay" fever. From the tree’s point of view, getting that pollen to female flowers capable of producing a nut is what it’s all about. Good pollen dispersal occurs under warm conditions. Wet weather, freezing temperatures and high winds can inhibit its successful spread.

You may not be especially fond of acorns, but other critters would beg to differ. More than 100 wildlife species are eager consumers and that includes not only the squirrels, deer, wild turkeys and bears, but also insects that lay eggs in the developing nuts and damage them before they can ripen and fall.

Deer hunters are another group that welcomes a heavy acorn crop. By late fall, acorns and other wild nuts can represent as much as 50 percent of a deer’s daily food intake and help the herd lay on fat stores for the winter. I wouldn’t bet on being able to fob your extra acorns off on the nearest hunting club, though. And I wouldn’t necessarily invite the deer over – when the acorns are gone, they’ll focus on their winter menu of woody shoots and buds, i.e., your shrubbery.

Does a heavy acorn crop say anything about the seasons to come? It’s not an indicator of a hard winter as some believe. Oak trees can’t see into the future and decide in spring (when pollination is occurring) that woodland wildlife will need to really bulk up before hibernation. They’re not altruists, after all, but concerned with their own survival.

We who wield the rakes and clear the paths of the profligate acorn crop are just by-standers watching nature going about its mysterious business. If an acorn falls in the forest, who cares? If it falls on your patio, it’s just another unasked-for “gift” from above.