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Seasonal Changes In Printed Leaves

Part of my love of natural dyeing and botanical printing is the flexibility that one learns to have in able to work joyously with these arts. The amount of rain that falls, the changes in soil nutrients, the time of season, where you gather your plants, every little change in nature has an effect on the results of your dyeing. But this is how nature works. She teaches us to bend like the willow and have the patience of an oak.

As much as I love nature for reminding me to try to live life with a bit more ease and spontaneity, I also really like to know how things work and WHY. I imagine I was one of those toddlers who drove their parents crazy with the constant questioning of “Why?” “Why do the leaves fall?” “Why is the ocean light blue near the shore and dark blue farther out?” “Why do I have to eat my spinach? I don’t want to look like Popeye!”

In almost every botanical print class I have taught, there has been at least one student to ask “When is the best time to gather your leaves?” My standard answer at first was, “Whenever they are available.” Printing with leaves can work any time of year, depending on the methods of printing you use. But, I also wanted to know the answer to this question. Is there a big difference between leaves gathered in the spring and leaves gathered in the fall?? What about dried leaves vs. fresh leaves? Now, I can’t answer this question for every type of plant out there, but I could at least take a look at a few.

First, let’s go over a bit about what is happening in a deciduous leaf as it grows. As the winter turns to spring, the days warm and the sun grows stronger. This triggers the production of chlorophyll in the leaves, giving them their green color and a chemical part of the process by which plants produce their food.

At the same time as chlorophyll is being produced, leaves are also producing chemicals called carotenoids and flavonoids. These are responsible for the yellows and oranges (and even some reds) in the leaves. But, because the chlorophyll is present in higher levels, it generally masks the yellow and orange colors in the leaves. That is, until fall.

With the coming of autumn, the days darken and the weather becomes cooler. Without the heat and sun, the levels of chlorophyll, carotenoids, and flavonoids begin to drop. But, lucky for us, carotenoids and flavonoids degrade at a slower rate than chlorophyll. With the chlorophyll breaking down more quickly, we are left with the carotenoids and flavonoids, giving us the firework display of colors so many of us look forward to in the fall.

Our final player in the fall color carnival is called anthocyanin (part of the flavonoid family). This chemical is responsible for our reds, purples, and magentas. However, it is only produced in the leaf once the weather begins to cool and the sugar concentration in leaves begins to increase. It is thought that these lovely deep shades of color help to protect the leaves from bugs that are otherwise attracted to the yellow colors left once the chlorophyll is gone. Anthocyanins may also help in protecting the leaves from sun damage which they are more prone to now without the chlorophyll. (Yes, you are right. There are a few trees out there that produce deep reds and purples even in the summer. Trees like Japanese Maples do actually make anthocyanins during the growing season.)

So, there we have our 4 most common chemical compounds that contribute to the colors of our leaves Now you ask, “but why do they fall off the tree?” Well, simply put, it’s to save energy. Producing those big leafy solar collectors takes a lot of energy for a plant. So they do it for the warm season, store up their food, and the rest for a bit in the winter. The drop in chlorophyll signals the leaves to produce chemicals that basically tell the tree to stop sending nutrients to the leaves and to let go of them (Let them goooo! Let Them Gooooo!)

Now, I wanted to know how these chemicals effect the results I could get with ecoprinting throughout the spring, summer, and fall. I set up an experiment and tried to minimize my variables (not an easy thing to do with nature). I mordanted 6 silk scarves in the same Aluminum sulfate bath and dried them well. Then, I gathered leaves from the same 6 trees in the middle of spring, summer, and fall. (No gathering in winter, ’cause… well… all the leaves had fallen.) I ecoprinted one of the silk scarves with fresh leaves each season. I also pressed and dried leaves from each of the plants for ecoprinting after 4 weeks of drying. Each scarf was steamed for 1.5 hours, unbundled, and left to cure for 3 days before rinsing and drying.

I chose leaves from 6 different plants: Sweet Gum, Muscadine Grape, a random Maple, Japanese Maple, Fig, and Dogwood. Some I know would produce color all year round and some I had not worked with. Some of these leaves (grape and maple, in particular) I knew would be high in tannin, or tannic acid. This astringent chemical is present in varying amounts, is closely related to flavonoids, and creates a brown color. It can act as its own mordant creating a strong bond with many natural dyes.

Below are my results. You will see the fresh leaf print on the left silk and the dried leaf print on the right silk. Within each silk you will also see a print of the top of the leaf (left) and underside of the leaf (right).

Sweet Gum – Spring
Sweet Gum – Summer
Sweet Gum – Fall
Muscadine grape – Spring
Muscadine grape – Summer
Muscadine grape – Fall
Japanese and random Maple – Spring
Japanese and random Maple – Summer
Japanese and random Maple – Fall
Fig – Spring
Fig – Summer
Fig – Fall
Dogwood – Spring
Dogwood – Summer
Dogwood – Fall (top – fresh leaf, bottom – dried leaf)

In general, the leaves produced more color as the year progressed. Dried leaves also produced deeper colors, possibly due to the degradation of the chlorophyll and higher concentration of tannins?

So, what does all of this mean? Nothing really, since these are only 6 plants out of millions, and a nature likes to keep us on our toes. But, I’ll probably still tell students to gather your leaves when they are available and for the most bold prints to try dried and/or fall leaves.