This Spring Brings Many Wildflowers to Mackinac Forests
Nature Notes
By Patricia Martin

It is truly spring. The snow is gone, birds are returning, and plants are growing. It's a wonderful time on Mackinac. This year we've experienced a mild winter (one with no ice bridge) and an early onset of spring. Things seem to be ahead of schedule. Heck, it isn't even Mother's Day and there are many different wildflowers blooming.

As many of my regular readers know, I love to ride my horse. Recently I had the opportunity to horseback ride in a beautiful spot, about 300 miles south of the Island at the Waterloo Recreational Area. Spring arrived there quite a bit earlier than it has up north. The leaves were opened on the maple trees and the flowering crabs, apples, and other fruit trees were already in full bloom (lilacs also). It was truly beautiful. Yesterday I rode my Grey on our first longish ride of the season to really get a good look at the condition of the woods. The Island's plants appear to be two to three weeks behind those of southern Michigan.

What causes the difference in blooming of the spring flowers and leafing out between Mackinac and 300 miles south? To answer this question, one has to understand the process of dormancy. Dormancy is considered to be arrested growth. It is essential to the survival of temperate herbaceous and woody plants. Because of the temperature extremes found in northern climates, plants would freeze if they didn't have a way to stop their growth and go into what is essentially a hibernation period to get through the winter. Changes in the environment cause the dormancy period to begin and to end. It is not a single factor that causes buds or seeds to break dormancy, but a combination of environmental changes. Warm weather is not enough, and that's a good thing. If temperature alone were enough, plants might start growing during an Indian summer in the fall or during a winter warm spell, only to be injured or killed with the next cold period.

There are three major factors that usually control the end of dormancy in both seeds and buds. These include temperature, day length (photoperiod), and water availability. To break bud, the plant must have the necessary temperature for a period of days and the correct number of daylight hours and/or dark hours. Plants also require a certain amount of water. In the winter, water is severely restricted owing to the fact that most of it is frozen. In the spring, much more water becomes available. In addition to day length, warmth, and water, many temperate plants require a period of cold weather in order to break their dormancy, and that process is known as vernalization. If you're familiar with tulips, you know that their bulbs have to experience a period of cold for about six weeks or they will not bloom. It is interesting to note that the beginning of dormancy in buds begins in midsummer, when water levels drop and the days begin to shorten.

The environmental factors, temperature, day length, and water, break dormancy because of their effect on a number of hormones in the bud or a plant. A bud is an embryonic shoot complete with rudimentary leaves, enclosed in bud scales. The scales protect the shoot from desiccation, restrict oxygen, and insulate the bud from heat loss. When the environmental conditions are right, a hormone called Abscicic Acid begins to decrease in concentration. This hormone is an inhibitor that turns off another hormone, IAA, which causes cell elongation, that is linear growth. As the concentration of IAA increases, the presence of ethylene, another hormone, increases, which causes radial growth. There are a number of other hormones involved in this process as well.

So basically the reason the Waterloo Recreation Area, and all of downstate, is further along in the growing season is that those areas are warmer, and photoperiods may be a bit longer than ours at this time, causing our plants to be a few weeks behind theirs in growth. The temperatures up here are decidedly colder.

As I mentioned before, I very much enjoy going out into the woods this time of year. The earliest of the leaves have just begun to come out on the trees. The poplars, particularly, have a wonderful shade of new green. It's a color that you can only see at the very beginning of the season. The leaf color will begin to darken as the plant produces more and more chlorophyll. Other leaves are appearing that have a reddish or coppery color to them. This is common in the cherries, service berries, and many plants in the rose family. This is because they have an additional pigment being produced called anthocyanin, which absorbs different wavelengths of light than chlorophyll. Anthocyanins usually appear during cooler weather in the spring and fall.

Spring is an unusual time of the year in that the light is fully reaching the forest floor, as the leaves of the trees have

not opened. With the abundance of light the early spring wildflowers have come up. Our woods are now alive with trillium, trout lilies, spring beauty, hepatica, cut-leaf toothwort, and Dutchman's breeches, just to name a few.

With the lack of leaves one can also see a lot further in the woods to notice the number of trees that have been knocked over by the winds we had this winter. The heavy snow in February and the strong winds of November and March certainly took their toll. There is evidence of wind throw everywhere. I don't think I rode on one trail yesterday that didn't have trees or branches down on it, or at least evidence of tree removal. In fact, I'd like to take my hat off to the State Park workers, who have obviously been working hard to remove the downfall from the trails and roads in order that we might more easily ride and walk in the woods.

I encourage you to get out into the woods as soon as you can because spring on Mackinac is a very short season and before we know it, it will be summer.

Trish Martin is a yeararound resident of Mackinac Island, has earned a master's degree in botany from Central Michigan University, and owns Bogan Lane Inn.