Besides the benefits listed in Mulching, mulches have other uses in the garden. They can cause some problems, too. Some further uses and problems are explored here
Preventing Frost Heaving
Because water swells as it freezes, alternate cycles of freezing and thawing garden soil cause “heaving,” or loosening of the soil. Heaving breaks plant roots, killing or damaging plants. Mulches insulate the soil to prevent freezing and thawing. For the best results apply a deep mulch after the ground has frozen. Remove the mulch after unmulched soil has thawed in the spring.
Permanent Mulches in the Vegetable Garden
In 1954, Ruth Stout (the sister of Rex Stout, the mystery writer) described in How to Have a Green Thumb Without an Aching Back her method of permanent mulching. She covered everything with straw and pulled it back to plant through it. The straw mulch kept the soil from compacting and kept weeds from growing. She never dug, never weeded, and had a highly productive garden.
Keeping Lawnmowers Away from your Trees
A circle of mulch around lawn trees benefits trees in two ways. While they are young, it keeps grass from competing with them for water and nutrients. It also keeps lawnmowers from skinning the bark off trunks. This type of bark damage (sometimes called “lawnmower blight”) prevents sap from moving from the roots to the trees and stunts their growth. Although the damage may look minor, it has serious and long-term consequences in the growth of the tree.
Harvesting Winter Root Crops
You can use your garden as a root cellar with a mulch deep enough to keep the ground from freezing. Time a crop of carrots, rutabagas, or another root crop so the plants will be ready for harvest as the soil begins to get very cold in the fall. Lay a thick layer of straw or another mulch over the plants. When you want to harvest in the winter, dig up enough mulch to expose a few feet of row and harvest the roots. If you cover the rows with straw bales, the bales can be tipped over to expose the soil easily.
Planting in Sod
Rather than remove sod to make a new planting bed, just lay mulch on it. Spray the lawn with herbicide to kill the grass and wait a week. Then mow the lawn as close as possible, spread a few inches of a mulch that decomposes rapidly, such as compost, and dig holes through the sod to plant flowers or shrubs. The herbicide breaks down in the soil so it doesn’t harm the plants.
To kill large areas of grass (or almost any other plant), cover it with black plastic mulch. The grass will die in a couple of months. When you remove the plastic, you will find bare soil covered by a layer of black decomposed grass, ready for planting. (This method doesn’t work with bermudagrass, couchgrass, or other grasses with extensive root systems. The grass outside the plastic keeps the root alive under the plastic.)
Planting in the Desert
Scientists in Israel developed a quick method of turning desert sand into productive garden soil. They applied a “mulch” of straw bales in rows on the sand, spread a couple of inches of soil on the bales and planted in the soil. Watered and fertilized with a drip irrigation system, the seeds sprouted and grew vigorously on the straw. Eventually, the straw decomposed and was incorporated into the sand to form high-quality garden soil.
Mulches can cause some problems if not managed correctly. Here are some hazards to avoid.
Some mulches might be fire hazards during dry weather. In areas where brush or grass fires are possible, select mulches that don’t burn readily. If there is immediate danger of fire, wet down the mulch thoroughly.
Mice like to nest in straw and hay mulches. To prevent damage to plants in the winter, either avoid the use of these mulches, or keep them pulled well back from the base of plants to avoid having meadow mice chew their bark.
Dense mulches more than 5 inches deep slow the movement of oxygen to the soil and carbon dioxide from the soil to the air, suffocating plant roots. If they cover a large part of the plants’ roots, they can slow their growth.
Mulches Against Bark
Deep mulch around the base of trees retains water and keeps the bark from drying out. This encourages fungus diseases like crown rot, which can kill even large established trees. Keep mulches pulled away from the base of trees.