Quite the Show: a Big Year for Seed Crops

By Maxwell McCormack

Northern Red Oak acorns.
(Quercus rubra L.)

     Keeping in touch with your woodlot is a continuing necessity for timely silviculture treatments, and for anticipating future conditions and needs. Monitoring seed crop cycles provides insight to natural regeneration dynamics. During 2016 we experienced a uniquely abundant crop of northern red oak (Quercus rubra L.) acorns. The crop from the oak stands on Mt. Megunticook, Camden Hills State Park, was so heavy that the early hikers this spring had difficulty finding secure foot placement. It was like trying to walk across a hardwood floor covered with loose marbles. Bright red radicles of ongoing germination were a subtle warning to step carefully.

     This summer, in our woodlot, I have spotted numerous first year oak seedlings in openings and along trails of an area harvested in February 2013. They have originated from the 2016 acorns. Tube shelters have been placed over many of them that have the potential for becoming saplings. With only three possible oak seed trees across the 5- to 6-acre area, the blue jays must have done their job well.

This year, many other tree species mirrored last year’s red oaks by producing a broad array of bumper seed crops. Most of our conifer, or softwood, species are to easy to spot because their female flowers are clustered in the crown tops. Male flowers, the pollen sources, occur in the lower portions of the crowns. This seems to be a way of nature to minimize self-pollination. By the time the dispersed pollen rises to the heights of the female flowers, it will have traveled laterally to adjacent trees.

     As cones mature, their color changes from green to brown and they drop into pendent positions so the winged seeds tend to drop out for dispersal. This year the white pines (Pinus strobus L.) are so heavy with cones that their upper crowns are deformed by drooping limbs. On the spruces (Picea A. Dietr.) there are heavy clumps of small, brown cones clinging to the sharp spire-like crowns.  

     For most of the conifers, the empty cones eventually fall to the ground. Balsam fir [Abies balsamea (L.) Mill.] is an exception. Fir cones form during a single season and remain attached to the branches in erect position. When they mature, the winged seeds, bracts, and scales shatter, leaving the axes on the branches. This is why you never find mature fir cones cluttering the ground.

     Many hardwoods also provided spectacular, seed shows. Red maple (Acer rubrum L.) is consistently fruitful, but this year many trees appeared close to death as the clusters of early, winged seeds obscured the emerging foliage. This species is one of the first to flower in the spring, but examine the flowers carefully. Some trees are entirely male, others are entirely female, some have both sexes. Seeds are dispersed in late spring to early summer. Sugar maple (Acer saccharum Marsh.), is also a good seed producer, but not as dramatic as red maple. You must look carefully in the crown foliage later in the summer to see the globular shaped seeds with slightly divergent wings that are dispersed in autumn.

In my view, the drama king this summer was American basswood (Tilia americana L.). Basswood flowers appear about the time of full leaf. They are not especially remarkable, but the honeybees work them enthusiastically. The fruit is pea-sized and distinctly spherical. It remains attached to a persistent 4- to 5-inch long, narrow, leaf-like bract. These bracts are lighter in color than the leaves, and flutter brightly in a summer breeze, much like the leaves of trembling aspen (Populus tremuloides Michx.). This past summer the basswood crowns were thick with bracts and, in full sun, trees could be determined beyond question from long distances. Basswoods are generally an indicator of rich, productive sites. Spotting them is helpful when developing management priorities.

Watch the tree flower-seed crop shows from spring through summer. Consider seedbed requirements, prepare some as appropriate, and plan some walks for spotting new seedlings. It’s fun -- a woodland treasure hunt. Tree ID books, field guides, and silvical characteristic references provide helpful information.