Preserving Fall Leaf Colors
Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent
If only we could capture the beauty of autumn and hold it to our hearts all winter long! One of the spectacular features of fall is the wonderful coloring of tree leaves. The more curious among us might wonder just how does fall color develop in trees? It's a story that's been told before, but here it is one more time.
The purpose of plant leaves is to harness the sun's energy to feed the tree. It does this by way of the chloroplasts in leaf cells. The chloropalsts contain the green plant pigment, chlorophyll. This pigment enables the leaves to capture the sun's energy to make sugars and oxygen from carbon dioxide and water. During the growing season the chlorophyll in present in abundant quantities. As the weather turns cool the fall and the days shorten, the leaves stop producing chlorophyll.
Some tree and shrub species are genetically capable of taking the carbohydrates left in the leaves and making them into anthocyanins. These are the red pigments responsible for the reds, pinks, and purples in leaves. As the chlorophyll begins to break down, the newly formed anthocyanins become apparent.
Other plants are not genetically capable of making the anthocyanins. When the chlorophyll breaks down in these plants, the leaves reveal the more stable orange and yellow pigments (carotene and xanthophyll).
Brilliant oranges come from a mix of anthocyanins along with the carotenes and xanthophylls. Trees that don't "perform" with remarkable colors lose all their pigmentation at one time and usually over a short span.
What are the weather conditions that favor the best fall color? Autumn weather that favors good production of soluble carbohydrates in the leaves will lead to more splendid fall coloring. Dry, sunny, and cool conditions but not lots of heavy frost are best for bringing out the reds, oranges, and bright yellows.
If plants that are supposed to show spectacular color, don't... then their location or general health may be the problem. Sunlight is generally needed for development of fall color, especially the reds. If a plant is shaded, development of fall color will be deficient. If the plant is experiencing stress, such as drought stress, fall color may be lacking. A plant that is not cued into the advent of fall because it's still growing vigorously due to heavy watering and fertilization late in the growing season, may also lack brilliant color.
Can you remember pressing brightly colored leaves between sheets of waxed paper to preserve their colors? It's one of those experiences of life that no one should miss. Here's how you do it. Place autumn‑colored leaves between two layers of wax paper. Cover with an old towel or cloth rag. Press the fabric with a warm iron, sealing the wax paper together with the leaf in between. Cut your leaves out, leaving a narrow margin of wax paper around the leaf edge.
Of course that's the old‑fashioned way of doing things. You can preserve fall leaves in your microwave oven. Choose fresh leaves with the brightest colors. You don't want fallen leaves that have already started to dry. Take separate leaves or small twigs and place them in the oven on top of two pieces of paper toweling. Cover them with one sheet of paper toweling.
Run the oven for 30 to 180 seconds. The drier the leaves, the less time they will need. Observe caution, as you could start a fire in your microwave if they "cook" too long. Be attentive. Leaves that curl after removal, have not been dried enough. Leaves that scorch, have obviously been left in too long. Let the leaves dry for a day or two and then finish the leaves with a sealant, such as an acrylic craft spray.
You may get even better results if you use the microwave and silica gel for drying. Place a 1.25 inch layer of floral silica gel in the bottom of a cardboard box. Place the leaves lying flat. Leaves should not touch and should be at least 1.25 inches away from the sides of the box. Cover the leaves with a 1.25-inch layer of gel. Place the uncovered box in the microwave. You want the microwave to operate at about 200 to 300 watts so if your microwave has 2‑10 settings operate it at level 4. If the oven only has three to four settings, it should be set at half. If your oven has a high to defrost options, set the microwave on defrost. Estimated drying time is 2.5 minutes if you're using a half pound of gel and about 5 minutes if using two pounds of gel.
Yet another way to preserve the leaves is to submerge them in a solution of glycerin and water. Use a mixture of one part glycerin to two parts water. Place the mixture in a flat pan, and totally submerge the leaves (in a single layer) in the liquid. You'll have to weight them down to keep them submerged. In about two to six days they should have absorbed the liquid and be soft and pliable. Remove them from the pan and wipe off all the liquid with a soft cloth. Done correctly, the leaves will remain soft and pliable indefinitely.
So take some time with the children in your life and go out and collect some of the treasures of fall. It's something they'll remember for the rest of their life... I know I have.