Grouppe Kurosawa: Organic Gardening - Reversing Plant Aging (print)

Reversing Plant Aging

When plants age, they stop growing and flowering and their leaves stop making protein and chlorophyll. Eventually, the leaves turn yellow and fall off, and the plants become susceptible to fungal (rust) infections and insect attack. Plant aging or senescence is a biochemical process that is highly susceptible to environmental conditions. It can easily be stopped by plant hormones, either made by the plants themselves or by soil microorganisms. If your roses stop flowering after two months, your plants are either aging prematurely, or they are not receiving enough light. The aging process of plants can be slowed dramatically by gardeners who understand why plants “shut down” biochemically. Plants can grow in a bucket of rocks if they are fed chemical fertilizers that contain water-soluble minerals. Unfortunately for plants, most minerals in the soil are not water-soluble. This means that most plant growth is controlled by soil microorganisms that break down organic matter into simple molecules that the plants can use. Although plants can make their own vitamins and amino acids, they can also take them up from the soil if microorganisms “pre-process” them first. Becoming a successful gardener does not require a degree in botany or horticulture, but it does require some knowledge of plant nutrition and how plants grow in response to their natural environment. This knowledge is freely available, but is generally “locked up” in the scientific literature in a form that is not readily understandable to the average person.

Milly’s garden soil is about 50% clay. It is terrible ground for planting. When she moved to her present house, we planted roses and numerous other plants, but they never did well. They stayed alive, but that was about it. About five years ago, a friend gave us a few pounds of a high grade fish meal for making soups and stocks. On a whim, we put two tablespoons of the meal in one gallon of water and fed it to the sickly rose bushes. The results were apparent within weeks. Milly’s roses started budding to an extent that is difficult to believe. The roses now bloom 8 months of the year, the leaves are lush green, and there is very little rust even though Milly lives on the edge of a fog belt (in Sonoma, California). Surprisingly, there have been no aphid infestations since the fish meal was first fed to the roses. We also treated the sick apple and pear trees that were present on the property when she bought it. Both trees were sparsely foliated with little fruit, the leaves were yellow and covered with rust, and the fruit was small, spotted with fungus and worm-ridden. Not a pretty sight. Milly wanted to have both trees cut down. We fertilized them with fish meal instead. One year after applying four gallons of a fishmeal suspension (2 tablespoons to one gallon water) to the base of each tree, both trees were lush green with foliage and have more fruit than Milly can possible process. There is no rust, and the fruit is completely worm-free. A plum tree that was planted 5 years ago as a small bare root sapling is now over 15 feet tall, and has so many plums that the limbs of the tree sag under the weight. It took awhile to find out why fish meal is such a good fertilizer at such low concentrations. The answer turned out to be more complicated than we originally envisioned.

First, this particular fishmeal works as a fertilizer because it is actually a human food product. It consists of fresh whole fish that are either too small to be filleted or they are the wrong species of fish. The fish are processed within 8 hours of harvesting in order to preserve freshness. The rapid cooking process stops the ammonification process, and other natural degradation processes that occur when a fish or animal dies. The intense steam heat stops the enzymatic breakdown of the fish organs and preserves the integrity of the plant growth factors in the meal. These growth factors, and the vitamins that are present in high concentrations in fish organs, are heat stable. The enzymes that break down growth factors into simpler compounds are not heat stable. The potency of the fish meal as a fertilizer has nothing to do with its high protein content. If that were true, chicken manure would probably work just as well. It doesn’t. Manure does not contain these molecules because they are absorbed out of an animal or bird’s food in their digestive tracts. In time, I found that the growth factors were actually precursors or biochemical building blocks for the group of plant hormones called auxins and cytokinins. Auxins control root growth and the elongation (not growth) of individual plant cells. Cytokinins stimulate plant cell growth, the synthesis of protein and chlorophyll, and induce budding and flowering. Cytokinins also stimulate the synthesis of molecules in plant leaves, stems and roots that protect plants from fungal and insect attacks. Auxins and cytokinins also work together to stop plant aging or senescence. Plants can make these hormones internally, but the hormones can also be made by a wide diversity of soil bacteria and fungi. When the hormones are secreted into the root zone by microorganisms, the plants will continue to grow and senescence will be postponed until the weather becomes harsh. The fishmeal does not contain preformed auxins or cytokinins, but it does contain very high concentrations of molecules that can be rapidly turned into these hormones by soil microorganisms. When we planted Milly’s roses, we packed the roots in fresh compost. Fresh compost contains a high concentration of microorganisms that break down organic matter, but not all organic matter is equally useful as a fertilizer. When fed fishmeal, the microorganisms produced plant growth hormones, and the rest is history. Plant compost does not contain these molecules because growth hormones are unstable and are not stored in plant tissues. They are naturally degraded very soon after they are made. High concentrations of auxins and cytokinins also block the activity of the plant enzymes that make the hormones in the plant cells. This natural feedback prevents plants from growing too vigorously. We can get around this “natural block” by inducing bacteria and fungi to make the auxins and cytokinins for the plants in the soil. After a great deal of experimentation, we found that bakers yeast, fed a diet of sugar and fishmeal, also makes cytokinins. A recipe for a simple, yet potent “Bug Juice” fertilizer in contained on this web site. Visit this essay and make your own feedstock for plant growth. It is fun and it teaches both kids and adults alike some of the principles of plant growth and development. Some people make beer in their basement. Organic gardeners can now make Bug Juice on their patio. Although we would not want anyone to confuse the two, they are both products of natural, organic processes.

Bon apetite.