STONE MULCHING IN THE GARDEN
J. I. RODALE
RODALE PRESS 1949
Chapter 1: Stone Mulches Under Trees
My dictionary defines a mulch as a layer of dried leaves, straw, etc., used to protect the roots of trees and plants. Actually, a much more comprehensive group of materials is intended when one thinks of mulches. Roll paper is made specifically as a mulch material. Even cinders have been used, but recently there came to my attention the use of stones, and the results were so amazing that this may seriously be considered for use in the small home orchard and garden.
In the July, 1944, issue of The Flower Grower there appeared an article by Walter J. Muilenberg describing an unusual experience with the Canada Hemlock (Tsuga Canadensis). In northeastern Michigan this tree is never found in pure stands. It is mixed in with hardwoods that protect it from the wind and sun. It seems impossible to transplant this species and make it grow under ordinary conditions.
- Muilenberg was clearing land and pulling out stumps when he came upon three hemlocks that he let grow. By accident stones were piled under one of them. That is the one that lived and became a wonderful specimen, vastly superior to the twisted and scraggly hemlocks usually seen in the forest.
Muilenberg says, “It is my guess that the third hemlock survived because of the rock, a weight of several tons, which had been piled around it. It had grown up in heavy woods, which consequently helped to make it more shallow-rooted, and in heavy shade, which helped to keep the soil cool and moist. Later, when the rest of the trees were removed, rock gave the tree a good grip on the soil and made for a cool, moist root-run, as rock always does. It would seem that the top of the tree will get along in good shape so long as the roots have protection.”
- Dr. I. K. Tuttle who had astonishing results with peach trees raised in the organic manner wrote: “I also have a lot of rocks lying under my prize trees. They hold the moisture in the ground and keep the hot sun from reaching the roots.
- Joseph A. Cocannouer wrote: “It was in Bavaria where I learned for the first time that stones spread over the ground between the rows of growing crops formed an excellent mulch for preserving the soil moisture.”
There must, therefore, be sufficient value in using stones as a mulch to make it worthwhile to experiment further. We have done this under two rather old apple trees recently. In connection with the planting of a new fruit orchard, we have stone mulched every other tree. The intervening trees were mulched with green matter. In a few years unpredictable advantages may show up in this orchard.
Thus far I have seen two advantages: First, a stone-mulch lasts much longer than a straw mulch. The latter is absorbed into the ground in a few years; then, through pressure of other work or carelessness, no mulch is applied and the weeds begin to flourish. One of the prime purposes of a mulch is to prevent the grass and weeds from growing under the tree, because this grass competes with the roots of the tree for nourishment. When an ordinary mulch is applied it does not take long before it has settled and the weeds begin to shoot through, thus defeating its original purpose.
Secondly, there are special situations in which this kind of mulch is irreplaceable. For example, we have tried to start young trees in a kitchen yard, but the poultry have always scratched under them and exposed the roots. Now we apply a stone mulch and the chickens cannot interfere.
- The most important benefit of a stone mulch lies in its moisture-conserving propensities. In addition the gradual disintegration of the surface of the stones adds fertilizer to the soil.
- Stones keep the air above them warmer, since they absorb heat and give it off slowly, lengthening the warm day considerably.
The lime rocks, especially, it seems, have the effect of warming up the soil. Experiments have shown that the difference between lime-loving plants and others is often nothing more than that the lime-lovers need more warmth. A difference of 27°F in April and 20°F in September near the ground as compared with the general air temperature has a great effect on the growing time of a plant that needs warmth. There may be still other reasons for the adopting of stone-mulches which will be discovered later.
- In preparing a seed bed for his garden a doctor sieved out stones, however tiny. An old man warned him to leave the small stones otherwise he would have poor and inadequate gardening results. He proved to be right and the doctor admitted it later.
- There are many plants that thrive in rock-gardens, benefiting from the dissolved rock which saturates the soil. Rock garden plants are rarely afflicted with disease.
- It is possible to apply compost without disturbing the rocks. If there is one class of tree to which you must apply the best and the most completely finished compost, it is to the fruit-bearers.
- Never use raw manure or partly finished compost under fruit trees. Direct the compost between the stones and hose it in if you can.