VOLUME 2 ISSUE 4 WINTER 1992

WHERE DO THEY COME FROM?

Have you ever seen native grasses or wildflowers show up somewhere you've never seen them before? Then you wonder where they came from. There are several possibilities, through some examples I will explore them.

I can't tell you exactly when the shift took place because I was away at school during those years, but the point is that it has converted back to native vegetation and the question is; where did it come from?

The most probable explanation in this situation is that those plants were there all along, but due to their constant disturbance they weren't ever able to develop enough to be recognizable. Just enough of the plant would grow vegetatively each year to sustain the roots in a weakened condition. Finally when they were no longer disturbed, the plants were able to gain a little bit each year until finally they started to produce flowers. In the mid-eighties the adjacent fields on our property were enrolled into the CRP and planted to switchgrass. I now burn the old school house lot in my regular prescribed burn rotation. The native plant response has been phenomenal since the introduction to fire. Big bluestem plants are ten feet tall, but the most rewarding was this winter after one of our 10 inch plus snow falls I flushed a 40 bird covey from the bluestem.

Another example I'd like to share is the occurrence of Liatris pycnostachya (gayfeather) near a pond, which is also on our farm. Initially when my parents purchased the farm this particular area was in row crops and there were a number of trees growing in the drainage where the pond is now constructed. The pond was built in 1974. At that time, true to typical government bureaucracy, trees were not permissible in or around a pond built for erosion control, so they were bulldozed. In 1989 we noticed the first blooms of gayfeather, fifteen years after the construction of the pond. Sitting here now and recollecting back to before the pond was built, it is difficult to know for sure just exactly whether the gayfeather is growing in former crop land or the area which formerly had trees. That makes it a little more difficult to surmise where the Liatris came from.

One possible postulate is the same as for the old school house lot. The plants existed in a weakened vegetative state for a number of years then finally gained enough vigor to bloom and be noticeable. If these plants are growing in the area once covered by trees then it could possibly be true. Once the trees were removed the plants were no longer suppressed. If that were true, why did it take so long for the plants to express themselves? If the plants had just been suppressed by the trees it seems they would have shown up sooner.

If the Liatris is growing in the area which was former row crop then this theory seems highly unlikely because of the annual cultivation. However that does bring up another possibility. In A Sand County Almanac, by Aldo Leopold, Mr. Leopold relates, "I once saw a power shovel, while digging a roadside ditch, sever the "sweet potato" root of a Silphium plant. The root soon sprouted new leaves, and eventually it again produced a flower stalk." This may be a possibility for some species of wildflowers and native grasses but in this case I don't think it applies. If you have ever transplanted Liatris you know that there is a bulb like structure just under the soil surface called a corm. It looks similar to a gall, the type commonly found on a stalk of goldenrod or ragweed, but is underground. Without the corm a gayfeather plant can't be started vegetatively. It seems that annual tillage would destroy the corms or at least never give them a chance to ever take hold, thus eventually dying.

The most likely explanation, at least to me, is seed. Seed from a soil seed bank. There is enough research available that we know numerous seeds exist in any given cubic foot of soil. Although a majority of the research that has been done relates to weed seeds (primarily because of their economic importance to agricultural crops) there are a few excerpts in the literature that pertain to native grasses and wildflowers. In addition, we know through seed tests done on native species seed sold commercially, dormancy is commonly associated with many native species. In a study conducted by J.W.T. Duvel, initiated in 1903, and reported by E.H. Toole and E. Brown, in the Journal of Agricultural Research, Volume 72, Number 6, Final Results of the Duvel Buried Seed Experiment, switchgrass seed which had been buried at 8 inches, still showed viability 20 years later. Thirty four percent of the total number of species originally buried grew after 39 years. It is no telling how much longer seeds would have remained viable after the 39 year project was completed. The same publication gives two examples of seed which germinated after long periods of storage, one after 147 years, the other after 158. The point in all of this is that seeds survive in the soil for many years, then, through a not fully understood set of circumstances, eventually germinate to perpetuate the species.

There are other ways which native plants can "show up" as well. Let's not forget probably the most common way plants spread, by hitching a ride. Whether it be by wind, water, fur or feather many plants get distributed by simple translocation. Why do you think stick tights stick so tight? I dismiss this as a possibility for our patch of gayfeather. If it were true, why is it only in one location? There are many other areas of disturbed soil close by, but no gayfeather.

Translocated soil which contains seeds and roots can also serve as a source. Many times I have noticed a couple of years after new highway construction the appearance of native plants which I know were not planted. I believe the disturbance of the soil put some seeds in position to germinate but I also feel that some of those plants could have come from remnant plant roots which were moved around during construction. The reduced competition then allowed the native plants to get a foot hold and flourish. Once again I dismiss this as an explanation for our situation. If it were true gayfeather plants would have been noticeable before pond construction, or the plants would have been present sooner.

What I have told you is not scientific by any means, however some literature does exist to give some credence to the explanations. I primarily wanted to give you several possibilities and some food for thought. My analysis of the whole situation is that if you get an immediate response to mechanical disturbance or a simple change in management practices the plants were present all along, just suppressed. If native plants show up after only a few years it could be from severed roots, translocated soil or soil seed banks. If plants show up after a long time it could be soil seed banks or possibly translocated seed. In reality, it is more than likely a combination of several of these processes.

Whether talking about seeds or plants, I would like to believe, since they are native, endemic species, they have an evolutionary adapted tenacity that allows them to patiently wait in the soil to eventually reclaim what was once theirs.