Wednesday, November 5, 2014

Mighty Oaks From Little Acorns Grow

“Mighty Oaks from Little Acorns Grow”, is a very old adage that has appeared in a number of versions, but is as true today as when it originated – apparently in the 1300s.

This year many of the oak trees in northcentral Pennsylvania had a fairly good crop of acorns; not a bumper crop, but there are still a lot of acorns on the ground. The variability of acorn crops mystifies a lot of folks, but it makes perfect sense when you consider it from the trees’ perspective. There are hordes of seed predators that eat acorns in any oak forest; from the large: deer, bear, and turkeys through the medium: squirrels, chipmunks, blue jays and wood ducks to the small: acorn weevil and acorn moth larvae that can infest up to 90% of the acorns in some years. These seed predators seem to be the primary reason oak, and most other, trees produce such variable crops of seed.

If seed production was constant the populations of the various seed predators would be stable and they would be able to consume all or almost all of the acorns; and so the trees have apparently evolved a mechanism to insure their genes will be passed on by producing widely variable amounts of seed. During years when acorn production is very low the seed predators’ populations tend to plummet. If, in a following year while seed predators’ populations are low, there’s a bumper crop of acorns, many will escape being eaten and germinate to produce seedlings. This is especially true because squirrels and jays tend to bury significant numbers of acorns in places that are ideal for the seed to germinate and grow but they do not retrieve all those buried acorns.
Red, white and chestnut oaks in our area were dropping acorns throughout the Big Woods this fall - 
Chestnut Oak Acorns

White and chestnut oak acorns mature the same year the trees flower; the acorns germinate soon after they hit the ground in the fall. Following germination the radicle (root) emerges, elongates and enters the soil.

The acorn then overwinters with its root in the ground, but waits until the following spring to develop an above-ground stem and leaves.
Chestnut Oak Seedlings - 1 year old
Red oak (and black, scarlet and pin oak) acorns take two years to develop from the trees’ flowers and wait until the spring after they fall to germinate and begin to grow.
Red Oak Acorns

Oak seedlings, unlike those of most other species of trees in the northeast, spend their early years growing a large root system and put minimal resources into top growth. They frequently spend anywhere from five to 15 years growing their root systems and only then begin to grow rapidly in height.   
White Oak Seedling - 8 years old
While the oak seedlings remain short they’re vulnerable to browsing by white-tailed deer. Where deer populations are excessive, repeated heavy browsing results in the seedling’s death and may result in total elimination of oak reproduction over large areas.  


1 comment:

molly said...

You can see why Beatrix Potter called her character Squirrel Nutkin