Natural Enquirer: Fall-Nature’s harvest time
Fall is equated with the time of harvest. Farmers are collecting their crops and back yard gardeners are canning, freezing or preserving the fruits of their labors. The highways seem to be lined with roadside stands offering everything from late season sweet corn, pumpkins, squash, popcorn and potatoes to apples, donuts and cider. It is a bountiful and enjoyable time.
The same thing is happening in the wild. The harvest is on. In order to understand what goes on in the fall, one must pause and reflect a moment as to why there is so much bounty at this time of the year. The answer is seemingly simple reproduction. As the harshness of the winter season closes in, nature has provided for the continuation of its plant species and therefore those that follow, the animals.
There are varied and numerous methods of plant reproduction, some so complex and interwoven that they appear to defy comprehension. Basically, however, there are four generalized methods. Roots or rhizomes extend underground from a plant, take root at intervals and send up a new plant above ground which grows, flourishes and repeats the cycle. On these roots may be large growths called tubers which store food for use by the plant (both old and new) throughout the winter and spring for use in growing new plants. (Yes, plants do continue to grow during the winter, albeit very slowly.) One of the most familiar of these tubers is our common potato, which, incidentally, came from Peru and not Ireland, with which it has been long associated.
In addition to root and tuber reproduction, a few plants extend their stems which, when they touch the ground, take root and form a completely new plant. This is sometimes called creeping or nodding stems. A very familiar plant with nodding stem reproduction is the black raspberry plant.
A more primitive form of reproduction which can be mentioned is through the production of spores rather than seeds. Our ferns and fungi reproduce in this manner as well as the scouring or horsetail rushes (sometimes called “snake grass” and “Indian bead grass.”)
By far the most common form of offspring assurance by plants is through the production of seeds. The method of dispersing these seeds is so varied and fascinating that it can hold one captive for hours on end, even if one does not get into deep contemplation as to the how and why of the forces of evolution to bring about a particular pattern. If one does begin to ask how and why, their entire life could be filled with study, inspection, speculation and awe of these seemingly insignificant potential forms of life.
If the plant happens to be suited for wet conditions, the seeds will then have developed special adaptations for dispersal by water. Many times, the seeds will have the capacity to float for extended periods of time. Wild rice, arrowhead and sweet flag all resemble strangely shaped bits of cork bobbing on the surface. The cow parsnip and marsh milkweed seeds appear as little rafts which are kept afloat for a briefer period of time by their displacement of the water surface. These plants also do not grow in the water itself, but along the edges. In addition, many of the aquatic plants reproduce by stems and rhizomes, which also tend to float when broken loose from the parent plant.
Water is also quite useful in the form of runoff and will carry all kinds of seeds down slopes.
Animals are unwitting carriers of a great many seeds through their need to feed on plants. Birds consume enormous quantities of cherries and berries which pass through their digestive systems with the hard coated seeds passing unchanged and being deposited a long distance from the parent plant. Grapes, elderberries, thistles, poke-berry, dogwood, raspberries, kinnikinnick and that nasty, thorny, exotic multiflora rose are dispersed mainly in this manner.
Large mammals do much of the same process as the birds whereas the smaller mammals either hoard their gatherings or bury the large hickory nuts and walnuts or acorns.
Animals also bump and trample plants, which causes the puff ball fungi to “puff out” their smoke-like spores or to dump the tiny seeds of the campions and columbines from their small vase-like pods. The jewelweed is one of the most intriguing of the “bump dispersers,” for the pods are “spring loaded” and literally burst explosively, shooting the seeds in all directions for many feet.
One of the more noticeable of the dispersal methods is through the “hitch-hiker seeds,” those that attach themselves to any object which brushes them. The familiar burdock, tickseed sunflower (beggars tick), cocklebur and tick trefoil are the most common. However, many of the mints, avens and even the large compass plant use this method from time to time. Imagine what a walking botanical garden a bison was, with his hairy coat just filled with seeds from the prairie he was grazing through. It is the “hitch-hikers” that you pull from your clothing after a walk in the fields and forest. How far from the parent plant have you carried the seeds?
Of all the ways of dispersing seeds, probably the wind is the most effective and universal. Seeds are constantly being bumped, blown, jiggled, slapped and even covered with earth after falling to the ground by the force of the wind. Windborne seeds have been carried to heights of thousands of feet and traveled hundreds of miles. That’s effective dispersing!
As would be expected then, a great many seeds have developed special modifications to aid in wind dispersal. We are all familiar with the light dancing of the milkweed “parachutes” but a large percentage of seeds also have winged or “feathering” appendages. Little blue stem grass, dandelion, goats beard, cottonwoods, aspens and thistles are a few of the “parachute” seeds.
Even some of the heavier seeds such as the maples and box elders have “wings” which provide for their helicopter-like spin to the earth. The majestic basswood seed has a similar effect but it is achieved by an entirely different structure. The elm family has wafer-like seeds which are also quite susceptible to the wind’s effect.
Disc shaped or flat seeds, such as the elms and prairie dock, have a unique ability, for if the seed drops after a snowfall and the surface is hard they will skitter across the slippery surface for considerable distances before lodging in a crack, crevice or tuft of grass.
Some seeds are so super small and light that they are blown about like the dust that they resemble, such as in the case with the diminutive mustard seeds.
When fall and winter arrive, there is seemingly very little to observe in the way of plant life. But wait-on your next outing take a closer look, for the evidence is there in the form of thousands of empty stems and pods, all mute evidence of nature’s way of providing “more.”
Peter Dring is a retired nature biologist and phenologist who lives in the Land O’ Lakes area. To comment on this story, visit the “Outdoors” section of StarJournalNOW.com.