The article “Let Fallen Leaves Lie,” published in The Columbian’s Life Section, Home & Garden on Nov. 19, couldn’t have been more timely. As a professional farmer, every year I see people picking up and throwing away one of nature’s best fertilizers and soil amendments.
For the past 20 years, I have been taking all of the thrown-away leaves I could handle to build up my soils. Deciduous trees produce and store all of their nutrients in their leaves. These are the nutrients that directly support the products of that tree.
When these leaves fall to the ground in the fall, they still retain these micronutrients that were needed to feed the tree. In nature, these leaves decompose and enter the soil structure, not only adding nutrients but also adding organic matter and, in many cases, adjusting the soil pH.
It took foresters many years to realize this. When foresters first started clear-cutting and burning slash and then replanting, they noticed that each time the new trees did not grow as well as previous plantings. In Mother Nature, if a forest burned, the first thing to grow naturally would be berries and deciduous trees, and over the years these trees would drop their leaves and rot down as fertilizer for a crop of new, strong conifers. If foresters today were able to shred the slash instead of burning it, this could be a running start.
Accurate Testing Vital
As professional farmers, if we want to test what nutrients a tree is getting, the old way was to test the soil around the tree, assuming that the tree is assimilating these nutrients in the soil. However, due to pH or other chemical combinations in the soil, tree roots may not be able to take up the micronutrients in the form that is in the soil.
PH is a measure of acidity or alkalinity in the soil, with a pH of 7 being neutral. Numbers below a pH of 7 are acidic, and numbers above reflect alkalinity. Some plants, like blueberries or azaleas, like acidic soil, where the pH is around 4.0 to 5.3. Most garden crops prefer a pH in the 5.7 to 6.5 range. If the pH is too low or too high, some soil nutrients are chemically tied up in the soil and cannot release themselves to the root system.
The most accurate way to analyze exactly what nutrients the tree is actually assimilating is to take a leaf analysis. When the tree leaves are most mature, in our area about the middle of August, leaves are collected and sent to an analytical laboratory. This test can tell a farmer exactly what nutrients are available to the tree. If needed nutrients are not getting to the leaves, and they are not being taken up by the roots, then the other option is to feed the leaves directly by applying nutrient to the leaves by spraying nutrients in a form that can be absorbed by the leaves.
—Joe Beaudoin
In my own research and testing, I have one field that I have leaf mulched over a period of about 15 years. The soil test analysis pH in that field started about 5.7, and the organic matter at about 2 percent. Currently the pH of that field has risen to 6.2 and the organic matter had tested up to 8 percent. I have done side-by-side tests with leaves and no leaves, and seen remarkable results even with the first applications. I have been growing apple trees for 60 years, and I have never had to fertilize a mature apple tree. I mulch all of the prunings and leaves right back into the ground, just like Mother Nature would do.
In my 75 years, I would classify leaf mulch as the best soil amendment no money needs to buy. Leaf them alone!
Joe Beaudoin owns Joe’s Place Farms in Vancouver.
