As the sunlight decreases, a chemical change begins to take place inside the plant where a corky wall of cells (called the abscission zone) forms between the twig and the leaf stalk. This corky wall eventually causes the leaf to fall off in the breeze later in fall.
Fall’s fiery tree colors are one of nature’s most stunning shows, but did you know those brilliant reds, oranges and yellows were hiding all summer long?
The vibrant hues you see when the leaves change isn’t about the weather getting cooler, it’s about a combination of sunlight, chemistry and the trees preparing for winter. After the autumnal equinox which happened on Sept. 22 this year, the days begin to shrink. The reduced sunlight tells deciduous trees and shrubs that it’s time to stop gathering energy and get ready for the winter.
All leaves contain different types of chemicals, but the chemical chlorophyll is responsible for absorbing sunlight, which turns to energy for the tree, and also gives leaves their green color. As the sunlight decreases, a chemical change begins to take place inside the plant where a corky wall of cells (called the abscission zone) forms between the twig and the leaf stalk. This corky wall eventually causes the leaf to fall off in the breeze later in fall. But as the corky cells begin to multiply, they eventually seal off the vessels that supply the leaf with nutrients and water, and it also blocks the exit vessels to some extent, trapping the simple sugars in the leaves. The combination of reduced light, lack of nutrients, and less water triggers the tree to start the process of breaking down the chlorophyll and then the green color fades. The green was “masking” the other natural pigments and as the green fades, you begin to see the leaves change color.
Yellow carotenoids, which give leaves their brilliant yellow and orange colors, exist in the leaf all summer long. Red anthocyanins, which gives leaves their red and purple colors, are freshly produced by the plants as fall ramps up. As autumn carries on, the leaves will begin to turn brown once all their nutrients are re-absorbed by the tree. The brown color is a result of leftover tannins, another chemical found in many leaves, especially oak leaves. The amount of moisture during the growing season will dictate just how vivid the fall color will be.
October is still a great time to plant new trees and shrubs in the landscape.
Ground temperatures are still warm, which means the root systems of the plants will still grow and get prepared for winter, you are not fighting the weeds, fungus or insects as you would in the spring and summer. Be sure to protect new trees with wire cages or fencing to stop deer from rubbing antlers and browsing. Move all tender plants summering outdoors inside before the first frost. Be sure to spray these plants with insecticidal soap before bringing them inside, to kill any insect pests. Now is also the best time for planting spring bulbs like crocus, daffodils and tulips. Be sure to dig a hole three times as deep as the bulb is long and add a tablespoon of bulbtone or bonemeal in each hole and cover with soil.
Check pH levels and if you have not done so, do a soil test in all garden beds to make sure your soil is healthy, with the right amount of nutrients and organic matter.
Collect a zip-lock sandwich bag full of soil, and take to the University of Maryland Cooperative Extension service. You will pay a small fee, but it is well worth the piece of mind and knowing that your plants will be healthy and can thrive.
If you have a vegetable garden, consider planting a cover crop once all the summer vegetables are finished. Crops like crimson clover or winter rye work well to prevent soil erosion and will add nutrients in the spring. Finally, apply compost, organic fertilizer and weed preventer as per package instructions. Put a thin layer of mulch, no more that 3 to 4 inches total to keep the additives in place and protect plant roots from winter damage.
Consider starting a compost pile with the fallen leaves from your yard. Composting leaves is one of the smartest things you can do for your garden. It’s a great way to improve your soil and add much needed nutrients the plants may have used during the growing season. First gather up all the fallen leaves from your lawn and flower beds, and if you can shred or grind them. This will speed up the decomposition process. Also add a compost accelerator, such as green lawn clippings, organic waste and organic kitchen scraps. Build your pile in layers by first putting down the shredded leaves, apply some garden lime, then add the green layer. Continue to build the layers until completed.
Turn the pile one or two times a week and continue to add green waste (grass clippings, kitchen waste, etc) as you turn. Turning the pile will introduce oxygen and will help it heat up and compost more quickly. Keep the pile moist, with the consistency of a damp sponge is optimum.
Then cover the pile with a plastic sheet, which will help retain the moisture and prevent it from drying out. By following these practices, especially turning and aerating the pile, you should have high-quality leaf compost by the following spring.
Happy Gardening!
(Editor’s Note: Ken Morgan is the owner of Robin’s Nest Floral and Garden Center in Easton, Md.)
