As we begin to brace for the winter cold, we find comfort in domestic warmth. The crackling of a fireplace, a bowl of warm soup, sipping hot chocolate after playing in the snow, or a dog resting in your lap while you read a book whose plot is placed in the Caribbean all can tide anyone over as the temperature outside flirts with freezing. Another common source of warmth in the winter months, and perhaps my favorite, is a cup of tea. But, after the leaves have been steeped and the liquid has snuggled your stomach, the loose tea can be put to more uses.
The main use of tea, other than for drinking, is for composting! This is the time of year when many home gardeners start to germinate seeds indoors to ensure healthy growth through the spring and summer months. By composting your winter tea, you are preparing for when those indoor seeds are ready to be planted in your outdoor gardens.
As tea leaves must moisten during the steeping process, they are preconditioned for breakdown in a compost heap. Tea leaves are also an excellent source of nitrogen, which can help to counterbalance all of the present food waste that is rich in carbon. Ideal compost has a carbon to nitrogen ratio of between 25-30 parts carbon to 1 part nitrogen. Too little nitrogen and the decomposition caused by microorganisms slows down, while too much nitrogen makes the compost reek as the excess nitrogen is converted into ammonia gas.
Before adding the used tea into a compost, make sure to remove the loose tea from its bag if the bag is not biodegradable. Paper bags will decompose, but polyester or nylon bags will not. Metal staples should also be removed from the bags.
For the plants themselves, the composted tea improves nutrient levels in the soil, which also increases the activity of earthworms and microorganisms that live in the soil. Because fresh tea grounds by themselves will increase the acidity of the soil, they should only be put directly into the soil of acid-loving plants, such as roses and ferns. Composting helps to dilute the acidity that the tea releases when water infiltrates the soil, but still maintains the benefits of adding loose tea to the soil.
The increase in acidity is caused by tannic acid. A unique feature of tea composting is the increase of tannins. When you taste the bitterness of tea, you are tasting the tannins. The same is true of red wine; the tannins leach into the wine from the wood barrels, as the bark of trees uses tannins to protect from fungal and bacterial infection. Unripened fruits and early leaves are high in tannins for their protection against hungry animals who dislike the bitterness, and from the enzymes and protein exudates of bacteria and fungi.
The brown colors of fallen leaves are also primarily the result of tannins that are exposed after the chlorophyll (green) disappears due to the reduction in daylight. The reduction in daylight and in chlorophyll informs the plant to begin a subsequent reduction in the permeability of the abscission layer of a leaf, or the corky layer of cells in a leaf that allows transport of carbohydrates from the leaf to the branch and allows the flow of minerals from the roots, by way of the branches, to the leaves. As the winter approaches, the leaves become a liability to the plant. The leaves no longer generate energy through photosynthesis, but would continue to require nutrients from the roots to stay alive. The leaves would also continue to respire, using carbohydrates and oxygen gas for energy, thereby releasing carbon dioxide and water vapor. So to be more efficient for the winter, when there’s a decrease of energy from the sun and a decrease of energy transferred among biota, the tree finds it evolutionarily prudent to shed its leaves. Like a squirrel storing acorns or a bear hibernating, the tree saves its energy for the upcoming colder months of relative scarcity.
After the xanthophylls (yellow), carotenoids (orange), and anthocyanins (red & purple) also disappear, the only pigments that remain in the leaves are the tannins (brown). Fallen leaves are the primary source of tannins for a forest. The fallen leaves decompose in the Spring, returning tannins to the soil for the roots to absorb and recycle.
Tannins readily bind with proteins, cellulose, starches, and minerals. The binding property of tannins can help to immobilize metals such as aluminum, reducing the toxic effects of metals upon the growth of roots.
By using tea in your compost, you have the potential to balance your carbon to nitrogen ratio, increase the activity of worms and microorganisms beneficial to soil health, strengthen your plants’ resistance to infections, grazing animals, and insects, and reduce the toxicity of the soil with the tannins present in your tea.
As I was in the midst of writing this blog, I felt the need to write a poem to organize my thoughts. I always find poetry allows me to condense my thoughts into a coherent flow. All of the metaphors and minute details are like individual flakes of tea that are collected together and then steeped within the simmering waters of language. After five minutes, I have a homogenous cup of hot tea ready for sipping. So, to conclude the piece, I’m leaving the poem in at the end for you to read.
During these cold days, we must act like the trees
whose excess is shed for efficiency, as our energy
wanes, staying indoors to sit by the fireplace, so too
does the outdoors brace, as trees lose their colorful leaves
laying a brown blanket upon the ground, yet we all know
that warmth is within reach, so let us all agree to increase
our productivity by recycling shared nutrients with germinating
seeds started indoors, then moved outside, to the gardens of our homes
whose soil is fed by the remaining matter found in our warm cups of tea
we can eat from our own waste, strengthening the bonds of being we need
to sustain our own livelihoods and the lives of other organisms in harmony
Can Tea Grounds Help a Plant Grow?
The Science of Color in Autumn Leaves