By Tom Worthley, Associate Extension Professor, Forestry UCONN Cooperative Extension
Wow, there were tons of acorns this past fall…literally tons. At least it seemed so, in my yard alone! There really were lots of acorns in many areas, and this phenomenon does occur every now and then, why is that? Why the great abundance of acorns (or hickory nuts) in some years and not others? I checked into some references for ecological characteristics of trees to seek some answers.
The first thing I found was that among the most common oaks in our area, even among trees of the same species in the same stand, certain individual trees are going to be more prolific seed producers than others. Also, abundant seed crops are cyclical. Even trees that normally produce abundant acorn crops don’t do so every year, and here is where it begins to get complicated. The cycle, or period between abundant crops of acorns varies dramatically from species to species. For example, black oak is reported to produce abundant acorns every 2-3 years, while chestnut oak produces a few every year, but in great abundance only every 4-5 years. White oak can take as long as 10 or as few as five years between good seed years. Red and scarlet oak are less reliable than black oak in that they may take as many as five years between abundant seed crops.
Weather in the spring also plays a role in acorn production. White and chestnut oaks produce acorns that ripen during the same growing season they are produced, and germinate in the fall soon after they drop. A warm week or so in the spring when flowers form (about the same time that leaves appear), followed by cooler than normal temperatures when pollination takes place will almost guarantee an abundant seed crop regardless of the cycle on these species.
Species in the “Red Oak Group” (red, black, pin and scarlet) on the other hand, require two growing seasons for the acorns to ripen and fall. Even then, the acorns overwinter under a light layer of leaf litter and germinate the following spring. So weather conditions two springs previously might have been a factor in this year’s acorn crop.
Deer, turkeys and other wildlife seek out the relatively-sweeter white and chestnut oak acorns as a fall and early-winter food source. Red oak acorns that must wait until spring to germinate are susceptible to predation throughout the winter by deer, turkeys, mice, squirrels, insects, birds, etc. During poor seed years 90 to 100% of the acorn crop might be consumed by wildlife.
Finally, in some years the upswing or down-swing portions of acorn-production cycles coincide for oak species (it would be fair to anticipate that this might happen every 6 to 8 years), and weather conditions in the spring might or might not stimulate abundant acorn production on the white and chestnut oaks. The result will be either a cautious autumn with “danger” from aloft, marbles underfoot and a herd of fat chipmunks running around or a season during which the wild turkeys will need to search a bit harder for their meals.