Mulching Landscape Beds

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Fall is a good time to mulch landscape beds. There are many benefits to using mulch in the landscape. Mulch reduces landscape maintenance and helps keep plants healthy. Mulch conserves soil moisture. Mulch helps reduce soil compaction and reduces water runoff and soil erosion. Mulch also prevents soil from splashing on plant leaves, which can result in soil-borne diseases. Mulch helps maintain a more uniform soil temperature (warmer in the winter and cooler in the summer) and promotes healthy soil ecology.

Mulched areas should be 2 to 4 inches deep (after settling). This is adequate to prevent most weed seeds from germinating. Mulch should be applied to a weed-free soil surface. Covering perennial weeds with mulch will not control them. Physically remove the weeds or control with non-selective herbicide before adding mulch.

It is best to mulch as much of the root zone of trees and shrubs as possible, but 3 to 6 feet is minimum. For beds, mulch the entire area. However, keep mulch from touching the base of plants. Just 1 to 2 inches is enough, to prevent bark decay.

There are a number of materials that can be used for mulching, and each has advantages and disadvantages. Traditional mulch materials are organic. The material should be weed-free, easy to apply, and readily available.

Organic mulches decompose with time. Decomposition releases nutrients and organic matter into the soil. The layer of mulch should be renewed as needed to maintain a 2 to 4 inch depth. On previously mulched areas, apply a 1-inch layer of new material. Pine straw will need to be reapplied each year while pine bark or shredded hardwood may not need to be replenished for several years.

Yard waste, such as grass clippings, leaves, and small twigs, can be used as mulch in moderation. The back side of the shrub border or natural area is an ideal place to dispose of small pruning clippings. Ideally, these materials should be shredded or composted before using.

Other organic materials that are sometimes used as mulch include wheat straw, shredded newspaper, peanut hulls, wood chips, sawdust, and partially decomposed leaves. Most of these materials are less expensive than pine straw, pine bark, or shredded hardwood but have some major limitations. I always recommend that fresh, light-colored, unweathered organic materials be aged for a 6 months to a year before applying. If not aged, these materials can tie up nitrogen during the early stages of decomposition.

Inorganic mulch materials, such as rocks and gravel, can be used as a mulch. These may seem like a good choice since they will not decompose. They do not require annual renewal, but they do pose some potential drawbacks. Be certain the material is compatible with the overall landscape design.

Light colored inorganic mulch materials can reflect sunlight and cause the temperature around the plants to be warmer. Rock mulch absorbs heat during the day and releases the heat at night. This can cause an increase in water requirement of plants. Avoid using rock mulch around plants that might not grow well under warmer, drier conditions.

Also with inorganic mulches, a border is needed to keep the material in place; otherwise rocks will be in the lawn, driveway or sidewalk. When leaves and other debris fall into rock mulches, they can be difficult to remove. If larger rocks are used, a leaf blower can keep the rock mulch looking clean.

Although there are many benefits to using mulches, there are also some potential problems. Some gardeners feel that if a little mulch is good, then more is better. This is not true. Excessive mulch, deeper than 4 inches, can suffocate plants roots and encourage voles. Voles are little field mice that gnaw on plant roots. To prevent vole problems, pull the mulch back 6 inches from plant stems. A circle of crushed stone about 6 inches wide around the trunk should help reduce vole damage.

Although it takes a little effort to apply mulch, it renews the look of the landscape and promotes a healthy environment for plants.