May/June 1988
By Peter Donelan
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BROWNIE HARRIS
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Nutrient leaf sprays can boost you garden's health and productivity.
RELATED CONTENT
Plant uptake of nutrients can be 100% to 900% more effective when the foods are applied to leaves rather than to soil.
Roots are leaves in the ground, and leaves are roots in the air.
—Alan Chadwick
As I wind my way down to our California hillside garden, I stop for a moment and examine a gray strand of Spanish moss that hangs from an oak branch over the path. This strange growth is not really a moss, nor is it a parasite leeching off its woody host. Instead, it's a plant without roots; one that feeds solely by absorbing nutrients dissolved in fog or rainwater through its clusters of threadlike stems.
Of course, our normal house and garden plants do have well-developed root systems for gathering nutrients from soil. Yet, like Spanish moss, they also have the capacity to feed through aboveground surfaces. Stems, buds, twigs and, most especially, leaves will readily absorb nutrients that are applied in a solution. So, in a real sense, leaves are roots in the air.
Foliar feeding is the practice of applying liquid fertilizers to plant leaves. This relatively new idea is fast becoming widespread. I recently worked at an organic research garden and minifarm. We relied on the soil's microbial activity to supply crop nutrients, but that process was slowed by the area's long, cool springs. So we began foliar feeding to stimulate plant growth early in the growing season.
The technique has many other applications. Some market gardeners now spray nutrients on fruit-setting crops like tomatoes and cucumbers to increase yields and on such leafy greens as lettuce and spinach to speed maturity and increase storage life. European grape growers use foliar feeds in their vineyards, and Chinese farmers similarly treat heading grain crops to increase yields. In our country, turf managers spray golf courses to help grass green rapidly, and some large commercial farmers use foliar feeds to prevent frost and drought damage. Other farmers spray regularly with liquid kelp to reduce aphid and red spider mite attacks or to control botrytis on strawberries and powdery mildew on rutabagas.
Fast Action
Leaves are green factories where the complex chemical processes of photosynthesis produce the compounds plants need for growth. Foliar fertilizers are absorbed right at the site where they will be used, so they are quite fast acting. Some gardeners have actually seen plants improve within an hour of spraying.
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