# Does Leaf Litter Insulate Soil?
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Winter and Summer
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It is not unusual for soil to freeze to a depth of several feet in the winter, or quickly lose all its moisture to the summer heat and wind. A layer of leaves acts as a blanket, allowing the soil to avoid the extremes. Frozen ground can experience what is known as frost heaves, which is when the water in the soil expands when frozen, forcing objects out of the ground. Shallow-rooted trees can have their root system damaged when this happens. With an insulating litter of leaves around the roots, the ice level goes down only a few inches, according to Paul Catanzaro of the University of Massachusetts.
Water Evaporation
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Water is primarily lost in soil through evaporation. As the sun heats and dries the top of the soil, aided by the wind, the water wicks up from the lower levels to replace it, and then is also lost. Rainfall is normally enough to replenish the lost water, but in times of drought more water may be lost than gained. An insulting layer of leaves on the soil keeps the moisture within the soil by preventing or slowing evaporation. The soil temperature is cooler under the leaves, according to studies conducted in 2007 by Jeffrey Engle at Seattle University, which keeps the heat from adversely affecting the rate of evaporation.
Spring Flowers
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One effect of the insulating value of leaves is seen in spring ephemeral flowers. They burst out of the ground in early spring while many other plants are still dormant. The reason why they can sprout so early is that the soil is warmer under the leaf litter than it is in planned gardens. They grow before the trees gain their spring leaves, and use the brief few days of sunshine and warmer soil to flower and reproduce.
Leaf Mulch
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Gardeners can take advantage of the insulating value of leaves by using them as mulch around their plants. Whether it is a vegetable garden in the height of summer or protecting shrubbery around the perimeter of the home, leaf mulch provides the same protection for the garden as it does for the woodland trees. Leaf mulch is free but should not be taken from the woodlands. The trees and ecosystem there depend upon its natural protection.
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