Too Many Acorns!

By Rebecca Roy, Conservation Education Coordinator

Recently I wrote a blog article about white pine cones, which we are seeing in really high numbers this year. In that article I mentioned that some other trees are producing way more seeds than typical. One of those are our beautiful oak trees. The drought laden, super hot weather in summer 2016 is responsible for this phenomenon too.

Oak trees come from two family groups--the red oak group, and the white oak group. Red oak trees have leaves with pointed lobes, while white oak leaves have rounded lobes. Red oak group trees are the most common oaks in Vermont.

Like white pines, red oak trees take two years to develop seeds. White oak trees develop acorns in one single season. So one factor in this really numerous acorn year is the trees all over producing as a reaction to the 2016 growing season, a very stressful and challenging growing season for all our trees because of the drought.

There is more to this story with oak trees, however. Oak trees have a pattern of acorn growth called masting. Acorns are a wonderful food source for many wildlife species--squirrels, Blue Jays, Turkeys, deer, mice, and bear all enjoy these nutrient rich tree nuts. In fact, wildlife enjoy this food source so much, that they would easily eat all the acorns every year given the opportunity. A single Blue Jay can cart away and store over 5,000 acorns a season! Trees have adapted a technique of having a heavy mast year every 2-5 years or so--which is a season where they produce way more acorns than normal. This heavy mast year is followed by years of more meager acorn production.

These mast years drastically affect wildlife populations--the numbers of mice, squirrels, and other small mammals are kept in check by many years of normal or meager acorn production. When a very heavy mast year occurs, the tree produces way more acorns than any wildlife in the area could ever consume. Some oak trees produce 10,000 acorns in a heavy mast year. This ensures some acorns will be able to thrive and grow into new oak trees. Over time natural selection has favored trees producing these cycles of acorns.

Trees expend lots of energy to produce the large number of acorns for heavy mast years. It takes so much energy in fact, that if you count the growth rings on a oak stump, you can determine heavy mast years because the rings are very narrow in those years. Oak trees do not grow very much in size during the years great energy is spent of acorn production.

One interesting thing I observed from a scarlet oak in my yard is that not only are there a much larger number of acorns this year, but the acorns themselves are also much bigger than normal. Take a walk in the woods near your favorite oaks and check out the acorns. I collected some to put under my bird feeders once the snow is a little bit deeper. Speaking of that, some old folklore predicts a snowy, cold winter after a heavy acorn mast year. This phenomenon is not scientifically proven, but fun to think about as I wax my skis. 

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