Mulching Simple & Beneficial
Mulching is one of the simplest and most beneficial practices you can use in the garden to enrich the soil and provide a better growing environment. Mulch is simply a protective layer of a material that is spread on top of the soil. Mulches can either be organic, such as grass clippings, straw, bark chips, and similar materials or inorganics such as stones, brick chips, and plastic. Both organic and inorganic mulches have numerous benefits.
Benefits of Mulching
- Conserve moisture, reducing the need for frequent watering
- Keep feet clean, allowing access to garden even when damp
- Keep fruits and vegetables clean
- Maintain a more even soil temperature
- Prevent weed growth
- Protect the soil from erosion
- Provide a "finished" look to the garden
- Reduce amount of week killer and other chemicals used, protecting children and pets
- Reduce compaction from the impact of heavy rains
Organic mulches also improve the condition of the soil. As these mulches slowly decompose, they provide organic matter which helps keep the soil loose. This improves root growth, increases the infiltration of water, and also improves the water-holding capacity of the soil. Organic matter is a source of plant nutrients and provides an ideal environment for earthworms and other beneficial soil organisms.
While inorganic mulches have their place in certain landscapes, they lack the soil improving properties of organic mulches. Inorganic mulches, because of their permanence, may be difficult to remove if you decide to change your garden plans at a later date. Therefore, this tip sheet is limited to the use of organic mulches.
You can find mulch materials in your own yard! Lawn clippings make excellent mulch. While not particularly attractive for a flower bed, they work wonderfully in the vegetable garden. The fine texture allows them to be spread easily even around small plants.
However, grass clippings are becoming scarce because of the increased popularity of mulching lawnmowers that provide many of the same benefits of mulching to lawns. Newspaper, as a mulch, works especially well to control weeds. Leaves are another readily available material to use as mulch. Leaf mold, or the decomposed remains of leaves, gives the forest floor its absorbent spongy structure.
Compost makes a wonderful mulch if you have a large supply. Compost not only improves the soil structure but provides an excellent source of plant nutrients.
Bark chips and composted bark mulch are available at garden centers. These make a neat finish to the garden bed and will eventually improve the condition of the soil. These may last for 1 to 3 years or more depending on the size of the chips or how well composed the bark mulch is. Smaller chips tend to be easier to spread, especially around small plants. Mulch can be purchased bagged or bulk.
Bulk may be cheaper if you need large volumes and have a way to haul it. Bagged mulch is often easier to handle, especially for smaller projects. Most bagged mulch comes in 3-cubic-feet bags.
Cherry Hill Township also provides mulch at its Richard E. Rohrbach Public Works Complex, 1 Perina Boulevard, free of charge. The township provides the mulch loose, and you will need to bring your own shovel and containers.
When to Apply Mulch
Time of application depends on what you hope to achieve by mulching. Mulches, by providing an insulating barrier between the soil and the air, moderate the soil temperature. This means that a mulched soil in the summer will be cooler than an adjacent unmulched soil; while in the winter, the mulched soil may not freeze as deeply. However, since mulch acts as an insulating layer, mulched soils tend to warm up more slowly in the spring and cool down more slowly in the fall than unmulched soils.
If you are using mulches in your vegetable garden or flower garden, it is best to apply them after the soil has warmed up in the spring. Cool, wet soils tend to slow seed germination and increase the decay of seeds and seedlings. If adding additional layers of mulch to existing perennial beds, wait until the soil has warmed completely.
Mulches used to help moderate winter temperatures can be applied late in the fall after the ground has frozen but before the coldest temperatures arrive. Applying mulches before the ground has frozen may attract rodents looking for a warm over-wintering site. Delayed applications of mulch should prevent this problem as, hopefully, the creatures would already have found some other place to nest!
Mulches used to protect plants over winter should be loose material such as straw, hay, or pine boughs that will help insulate the plants without compacting under the weight of snow and ice. One of the benefits from winter applications of mulch is the reduction in the freezing and thawing of the soil in the late winter and early spring. These repeated cycles of freezing at night and then thawing in the warmth of the sun cause many small or shallow rooted plants to be heaved out of the soil. This leaves their root systems exposed and results in injury or death. Mulching helps prevent the rapid fluctuations in soil temperature and reduces the chances of heaving.
How to Calculate the Amount of Mulch Needed
To determine how many cubic feet of mulch is needed, you need to calculate the surface area and the desired depth of coverage. There are 27 cubic feet in a cubic yard. One cubic yard will cover a 324-square-foot area with an inch of mulch. Figure out the square footage of your bed, that is the width times the length for square or rectangular shaped beds. The square footage of a circular bed is the distance from the middle of the circle to the outside, multiplied by itself and then multiplied by 3.14 (which is pi).
Multiply your square footage by the depth desired (in inches) and divide by 324 square feet. This will tell you how many cubic yards you will need.
How to Apply Mulch
Before applying any type of mulch to an area, it is best to weed the area. Spread a layer of mulching materials over the entire plant bed. Keep mulch 2 to 3 inches away from the stems of woody plants. This will prevent decay caused by wet mulch and rodent damage during the winter. Keep mulch 6 to 12 inches away from the walls of buildings.
Subterranean termites nest in the soil and feed on materials that contain cellulose. Termite treatments are applied to the soil around buildings, so keeping mulch away from walls will prevent termites from using it as a bridge to cross treated soil.
Newly planted trees require a circle of mulch 3 to 4 feet in diameter. Maintain this for at least 3 years. Do not pile mulch against the trunk. For established trees in lawns create a circle of mulch about 2 feet in diameter for each inch of trunk diameter. Increase the size of the mulched area as the tree grows. Try to apply the mulch at least 6 to 12 inches beyond the drip-line of the tree. Because the root system can extend 2 to 3 times the crown spread of the tree, mulch as large an area as possible.
How Deep to Apply Mulch
The amount of mulch to apply depends on the texture and density of the mulch material. Many wood and bark mulches are composed of fine particles and should not be more than 2 to 3 inches deep. Excessive amounts of these fine-textured mulches can suffocate plant roots, resulting in yellowing of the leaves and poor growth.
Coarse-textured mulches such as pine bark nuggets allow good air movement through them and can be as deep as 4 inches.
Mulches composed of grass clippings or shredded leaves should never be deeper than 2 inches, because these materials tend to mat together, restricting the water and air supply to plant roots.