High-Hanging Fruit: Boom and Bust Seed Crops of Conifers

High-Hanging Fruit: Boom and Bust Seed Crops of Conifers

For portions of two days, I watched a red squirrel clipping and caching cones from the crown of a towering white spruce. It was a bumper crop that season, and thousands of cones hung in bunches throughout the tree. The squirrel seemed intent on visiting every bunch in the upper branches as it feverishly clipped and cast cones down to the forest floor. I was curious and counted all the cones I could find lying beneath the tree. I came up with 235 before I quit, and there were hundreds more that landed on the branches above me. Researchers have found that a hard-working squirrel can clip and store upwards of 12,000 ripe, unopened cones before seedfall.

Conifers produce cone crops erratically; there will be years of complete cone failure, years of poor to moderate cone production, and, periodically, years in which a staggering number of cones burden the trees. In such a year, our squirrel’s single white spruce may produce 10,000 or more. Bumper mast years produce such an excess of cones that predators can’t possibly consume them all – guaranteeing the tree opportunities for successful seed dispersal, germination, and recruitment. The relationship between mast crops and the animals that feed upon their seeds is a remarkable, though not fully understood, phenomenon. For example, ecologists have noticed that prior to a bumper cone crop, squirrels may produce an additional litter of young, presumably to benefit from the surfeit of food later on. What tips the squirrels off? One theory suggests that the over-abundance of male pollen cones in the spring cues the squirrels, causing them to increase their reproductive output and hence benefit from the bonanza of cones that will follow by summer’s end.

Vertebrate cone seed predators in our region include red squirrels, red-backed voles, cedar waxwings, black-capped and boreal chickadees, red-breasted nuthatches, common redpolls, white-throated sparrows, pine grosbeaks, and pine siskins. Of course, others occasionally take part, too. During a period of severe food shortage on Baccalieu Island in Newfoundland, red foxes were seen climbing balsam fir trees and eating the cones. In the West, scrub, stellar, and pinyon jays, along with Clark’s nutcrackers and pine squirrels, collect and cache millions of pine seeds, and grizzly and black bears dig up and consume many of these nutritious, oil-rich food stores.

Native peoples throughout North America have used conifer cones in many ways. Seeds were ground up and made into a powder that served as a delicacy when mixed with deer fat. Dried juniper berries were mixed with fish oil or animal fat, as well as with other fruits, such as mountain cranberries, and made into the original PowerBar. Juniper berries were also brewed as a hot beverage. When all else failed, green twigs and cones of spruce were boiled in maple syrup to produce a potent beer. Medicinally, spruce cones were relied upon to cure toothaches, indigestion, diabetes, hyperactivity, fever, pneumonia, arthritis, colds, snake bites, tapeworms, and urinary problems. An all-purpose apothecary for breeding was helpful for contraception, inducing labor, assisting women after childbirth, and curing venereal diseases.

Cones come in a variety of shapes, from globose to ovoid to cylindrical; they may have blunt or pointed ends, and they may point up, like the firs, or down, like the spruces, hemlocks, and white pine.

Not all cones are seed cones. Seed cones are the female fruits of conifer species, and a typical seed cone’s woody scales cover and protect the ripened ovules underneath them. Seeds are impressed against the inner wall of each scale. In the case of our squirrel’s white spruce, there are two seeds per scale for a total of approximately 130 seeds per cone. Though they don’t look the same, the male reproductive organs that provide pollen are also considered to be cones. They are found on the lower branches of most conifers or on the tips of juniper branches. (Most species of juniper are dioecious, meaning that a particular plant has male or female cone flowers on it, but not both). Male flowers are exquisitely intricate and colorful.

What follows is a look at some of our region’s cones.

High-Hanging Fruit: Boom and Bust Seed Crops of Conifers Image

Creeping Juniper
Juniperus horizontalis

Draped over rocky outcrops on coastal headlands and cliffs in Maine and southeastern Canada, creeping juniper is a low prostrate shrub that instantly impresses upon us that life is indeed tenacious and heroic at times. The same species bravely occupies exposed serpentine slopes and ridgelines in both eastern and western mountains. The powdery blue-to-blackish berries are the pollinated female cone fruits whose fleshy scales have fused together and are covered with a resinous coating. The slight ridges and bumps that we see on a berry’s otherwise smooth surface are all that can be seen of the woody scales that enclose seeds.

Juniper berries are relished by red squirrels, chipmunks, coyotes, foxes, ruffed grouse, willow ptarmigan, downy woodpeckers, black-capped chickadees, and yellow-rumped warblers and are a preferred food for robins, cedar waxwings, and evening and pine grosbeaks. I have seen creeping juniper seeds in the scat of black bears in Canada’s Northwest Territories. Notice the lovely orange male pollen cones on the foliage tips of the creeping juniper photograph that accompanies this description.

High-Hanging Fruit: Boom and Bust Seed Crops of Conifers Image

Tamarack
Larix laricina

Eastern tamarack is technically a conifer or evergreen, though it completely loses all of its needles in the fall. Among dark, black spruces the luminous yellow autumn foliage of tamaracks lights up the boreal north woods, as well as New England and New York’s sub-boreal and northern mixed hardwood habitats, where poorly drained wetland soils support their growth. Tamarack and others of the Larix genus boast the most northerly distribution of any conifer on earth. Tamaracks thrive at the tree line in Quebec and in Labrador’s subarctic barrens, where they stand smallish, but as trees, in contrast to the black spruces, willows, and birches, which appear dwarfed and shrub-like, if not flat-out prostrate, in such environments. Erect, immature seed cones are the color of a red Bordeaux wine, and they mature to be pale tan. They are ovoid to globose in shape, more egg-shaped when immature, more round when mature and fully opened. Willow ptarmigan and spruce and ruffed grouse eat tamarack buds and new needle shoots, while red squirrels, robins, purple finches, pine siskins, and crossbills eat the seeds.

High-Hanging Fruit: Boom and Bust Seed Crops of Conifers Image

White Cedar
Thuja occidentalis

White cedars clinging to limestone cliffs are picturesque with their upsweeping branches and fan-like sprays of foliage. White cedars are among the Northeast’s longest-lived trees; some specimens range from 500 to 1,000 years old, and deceased trees have been calculated to be nearly 1,900 years old. Also known as arbor vitae, the white cedar has small, attractive oblong cones, especially appealing when they are yellow and immature (as seen in this photo). Tiny seeds inside are dispersed by wind and carried away from the opening cone on two long, lateral wings. Robins, pine siskins, house finches, and common redpolls are known to eat the seeds. Dozens of species of birds and mammals benefit from the protective cover of white cedars.

High-Hanging Fruit: Boom and Bust Seed Crops of Conifers Image

White Spruce
Picea glauca

White spruce can be found in an extraordinary diversity of northern habitats, from Maine to Labrador’s coastline, across the continent to the Northwest Territories and interior Alaska, north to the tree line. Disjunct populations of unique white spruce “varieties occupy habitats as diverse as South Dakota’s Black Hills, western Wyoming, and scattered locations in Alaska.

The following species of mammals and birds feed on the seeds of the cylindrical, rusty-brown seed cones: squirrels, chipmunks, voles, mice, red crossbills, white-winged crossbills, pine siskins, red-breasted nuthatches, boreal and black-capped chickadees, cedar waxwings, wood and Swainson’s thrushes, pileated, hairy, and downy woodpeckers, evening and pine grosbeaks, purple finches, white-throated sparrows, and mourning doves. Even mallard ducks are known to feed on white spruce seeds.

High-Hanging Fruit: Boom and Bust Seed Crops of Conifers Image

Balsam Fir
Abies balsamea

Henry David Thoreau described the dark pyramidal silhouettes of balsam fir as “plumes plucked from the raven’s wing.” Dark and shadowy against the glow of neighboring hardwoods, they are enchanting embodiments of the north woods. Everything is special about this tree: its soft, lustrous aromatic foliage, its striking shape and symmetrical form, the way it punctuates the view at the bend of a wild river.

Balsam fir grows best in cooler, moist organic soils, around wetlands, and climbing to the higher terrain of most northeastern mountains. Erect seed cones are two to four inches long, cylindrical in shape, and purple or dark purplish-green when immature. They are rarely seen unless you look down upon fir crowns from above. Weather, birds, and squirrels pick at the cones and contribute to their natural habit of disintegrating, scale by scale, leaving only the central axis shaft of the cone to be seen after the scales and their seeds have been scattered to the forest floor.

High-Hanging Fruit: Boom and Bust Seed Crops of Conifers Image

Jack Pine
Pinus banksiana

Serotinous species, like jack pine and black spruce, have persistent cones that remain on the tree for years. Such cones are sealed shut with a thin film of resin until a forest fire in the understory melts the seal and releases the seeds to repopulate the burned forest. These fire cones open only when the temperature climbs to 122 degrees. Ripe seeds may wait and remain viable within their cones for decades before fire frees them to fall to the earth. Other cones on the same tree may open and shed seeds during hot, dry weather, with the result that both persistent and open cones may be seen on any jack pine or black spruce.

Short, twisted needles, contorted trunks, gnarly branches, and the presence of messy-looking, persistent cones throughout the crown detract from the aesthetic qualities of this species. One of my botanist heroes, Russell Peterson, described the jack pine as “scrubby, scruffy, and terrier-like.” Still, the accompanying photo of jack pine’s lovely male pollen cone flowers (on the left, accompanied by a female seed cone on the right) shows there is beauty, too. The magnificence of this species is the role it plays in its environment. It is the most northerly pine in North America – growing up to the boreal forest and arctic barrens, where it provides extensive vital cover and lichen food habitat for thousands upon thousands of wintering caribou.

High-Hanging Fruit: Boom and Bust Seed Crops of Conifers Image

Black Spruce
Picea mariana

The sharply columnar spires of black spruce make this my favorite tree. Though I had never met them as a very young child, I nonetheless identified with their boreal muskeg and subarctic habitats, and yearned to be there – sled dogs, caribou, wolves, and all. Black spruce’s ovoid-shaped cones are unusual, not only for their habit of persisting in patient preparation for fire, but also for the stout, curved stems (see photo) that attach the cones to the branches. No doubt these rugged stems help prevent wind, snow, and ice from prematurely detaching the cones. A number of small mammals and birds eat the seeds, pollen cones, new needles, and buds of black spruce, including red squirrels, voles, chipmunks, spruce and ruffed grouse, willow ptarmigan, hairy and downy woodpeckers, black-capped and boreal chickadees, American robins, cedar waxwings, wood thrush, evening grosbeaks, white-throated sparrows, purple finches, pine grosbeaks, pine siskins, and red- and white-winged crossbills.

 
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