The catalpa tree in my front yard did just that in one year.

My research for this topic began last fall. The catalpa tree is an ornamental, with heart-shaped leaves varying in size from 4-10 inches in width.

One night after a hard frost, every leaf dropped presenting a perfect circle of leaves piled 3-4 inches high directly under the branches. I wanted to determine the weight of all the leaves produced by this tree because the leaves grow to full size in less than one week. Where else in nature does such a huge weight gain occur in such a short time? I suspected the weight must be impressive. Since over one-half of the circle of leaves had fallen over shrubs and garden plants, I chose to rake a section of the circle resembling one quarter of a pie which lay on the lawn and driveway. The leaves were placed in three large black trash bags where they were left to thoroughly dry over the winter.

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Last fall, leaves from the catalpa tree in the author’s front yard were gathered, dried and weighed.

Photo by Robert M. Ungerer

The same tree full of leaves this past summer.

Photo by Robert M. Ungerer

Since the leaves were neither fully dried out or fresh green summer leaves I could not weigh them for an accurate total weight at that time. To begin this project, the three bags of dried leaves were weighed on a bathroom scale subtracting the tare weight of the bags. The weight was 33 pounds which represented roughly one-fourth of the total leaves that fell from the tree.

Therefore, the expected total weight of all the leaves, if dry, should be 4 X 33 or 132 pounds. When the leaves were living on the tree they were fresh, green and contained water.

Next, I had to determine the percentage of water in each leaf as well as the percentage of dry leaf structure consisting of cellulose, protein and carbohydrate in each leaf. I selected 100 representative dry leaves which weighed 5.6 ounces. Likewise, 100 representative fresh green leaves weighed 9.75 ounces. Subtracting the dry leaf weight from the fresh green leaf weight equaled 4.5 ounces of water in every 100 leaves.

Therefore, 4.5 ounces of water in 9.75 ounces of fresh leaves or 4.5 divided by 9.75 equaled 43 percent water in the average leaf no matter how many leaves were counted. More importantly, since my leaves were dry, I needed to know the percentage of the dry leaf material in the fresh green leaf. If 43 percent was water, the remaining must be dry leaf material or 57 percent. Since the catalpa tree produced 132 pounds of dry leaves in one year and 132 pounds represented 57 percent of the total weight of leaves, the expected total weight of fresh green leaves was calculated by dividing the weight, 132 pounds by 57 percent, which equaled 232 pounds of fresh green leaves.

Mature deciduous trees (lose leaves in the winter) of many species can be expected to produce a similar weight of leaves. I found the fact that trees produced leaves weighing over 200 pounds in a short time each spring a marvel of nature. During the summer these 232 pounds of leaves also produced, through photosynthesis, solid wood growth as annual rings visible on cross section of a tree limb.

So what is the significance of huge leaf production of mature trees around the world? I present some random facts and information. Leaves absorb carbon dioxide from the atmosphere and water from the ground and atmosphere to produce glucose and oxygen using energy from the sun through the process of photosynthesis. Studies reveal that two mature trees can produce enough oxygen for a family of four to breathe annually. An acre of trees can absorb annually the amount of carbon dioxide produced by driving an average automobile 26,000 miles.

The media has educated the public about increasing carbon dioxide contributing to global warming. Tree leaves absorb carbon dioxide so while a solution is complex, I suggest planting a tree or better yet plant several right now.