WHERE TO USE MULCH AND PINE NEEDLES

Mulch entire beds of shrubs, trees, annuals, perennials and/or ground covers. Mulching is an extremely important practice for establishing plantings. Mulch helps to conserve moisture in the root ball of the new plant until it establishes roots in the adjacent landscape soil. Mulch also helps discourage weeds that can compete with new plantings for water, nutrients and light.

Mulch can be used instead of grass around individual trees and shrubs in a lawn. This greatly reduces the competition for water and nutrients from the turf and increases the growth rate and health of trees and shrubs. When placed around plants in a vegetable garden, mulch can help to conserve water and control weeds.

In addition to being useful around plants, mulch can be used as a ground cover for walks, trails, driveways, and play and natural areas. It can be used temporarily to cover low-growing tender plants to protect them from frost injury. Mulch also can be composted and used as a soil amendment.

WHEN AND HOW OFTEN TO MULCH

Mulch can be applied around established plants at any time. Newly-set plants should be mulched after they are planted and thoroughly watered. Because of the abundance of leaves and pine needles, fall is an excellent time to collect leaves and other yard trash for mulching plants.

Organic mulches will gradually decompose and need replenishing to function effectively as a mulch. Shallow plant roots grow up and into moist mulch and they will die if the mulch is allowed to decay or wash away. How often mulch needs to be replenished will depend on the mulching material. Grass clippings and leaves decompose very rapidly and need to be replenished frequently. Other organic mulches such as cypress mulch, pine bark and wood chips break down very slowly and need only be replenished every year or two.

Once plants in a ground cover or shrub bed have formed a solid mass by touching one another, the mulching requirement is reduced. The plants create their own mulch by dropping leaves, flowers and fruit. Leaves from surrounding trees also may fall in the beds and provide additional "free mulch." Most organic mulches will change from their original colors to a weathered grey color with age. There are several ways of restoring color to mulches. One approach is to apply a thin (1 inch or less) layer of fresh mulch to the surface of the existing mulch. This approach is labor intensive, expensive and can result in an excessively thick mulch layer. Another approach is to shallow rake the existing mulch to restore a freshly mulched appearance. A third choice is to use a mulch colorant. Mulch colorants are dyes that are sprayed on the mulch to restore its color. Manufacturers claim they are harmless to both plants and animals, but applicators should use them cautiously as they can cause skin and eye irritation.

Inorganic mulches such as gravel, pebbles and stones are considered permanent mulches and rarely need replenishing. Still, small particles will eventually move down into the soil and a thin layer of gravel will need to be added to the existing layer of gravel. Leaves and other debris also need to be regularly removed from the top of these materials to maintain a neat appearance.

HOW TO APPLY MULCH

Mulch entire plant beds with a layer of mulching material. When mulching individual 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.

Pull mulch 1 to 2 inches away from the stems and trunks of plants. The high moisture environment created by mulch increases the chances of stem or trunk rot which can result in plant death.

HOW DEEP TO APPLY MULCH

The amount of mulch to apply will depend on the texture and density of the mulch. Many wood and bark mulches are composed of fine particles and should not be more than 2 to 3 inches deep after settling. Excessive amounts of these fine-textured mulches around shallow-rooted plants can suffocate their roots causing chlorosis and poor growth. Course-textured mulches such as pine needles and pine bark nuggets, which allow good air movement through them, can be maintained as deep as 4 inches.

Mulches composed solely of shredded leaves, small leaves (oak leaves), or grass clippings should never exceed a 2-inch depth. These materials have flat surfaces and tend to mat together, restricting the water and air supply to plant roots.

HOW MUCH TO BUY

Pine Straw:  NC long needle (1 bale covers approximately 35 sq ft)

If you are going to buy mulch, you need to calculate the area and the desired depth of coverage to determine how many cubic feet of mulch you should purchase. Bulk quantities of mulch are sold in cubic yard volumes.

First, determine the square foot measurement of your shrub or tree area(s) to be mulched. For instance, if you have a shrubbery border 4 feet wide and 25 feet long, the area to be mulched equals 100 square feet (4 feet x 25 feet = 100 square feet).

Next, if you are going to apply mulch 3 inches deep to this area, convert the 3 inches to a fraction of a foot. Three inches divided by 12 inches equals 1/4 foot, or .25 feet. Multiply this fraction by the square foot measurement of the area to be covered. For this example, you will need 25 cubic feet of mulch (.25 feet x 100 square feet = 25 cubic feet).

One cubic yard equals 27 cubic feet (a cubic yard measures 3 feet by 3 feet by 3 feet; 3 feet x 3 feet x 3 feet = 27 cubic feet). In the shrubbery example just given, you need 25 cubic feet of mulch, which is 2 cubic feet less than one cubic yard.

Before you purchase mulch in bulk (i.e., buy an entire cubic yard), compare the cost with purchasing your mulch in smaller units.

Bagged mulch is also available in amounts such as 1.25 cubic feet or 2.0 cubic feet. If you purchase the mulch needed for the shrubbery example given above in amounts of 1.25 cubic feet, you will need 20 bags (25 cubic feet r 1.25 cubic feet = 20 bags).

If you purchase bags of 2.0 cubic feet, you will need 12.5 bags (25 cubic feet r 2 cubic feet = 12.5 bags). Therefore, you will purchase 13 bags. However, as discussed above, always remember to pull mulch 1 to 2 inches away from the stems and trunks of plants to lessen the chances of stem or trunk rot. So, whether the shrubs are single or multi-stemmed, you will not need all of the mulch determined above; the calculations did not include either the area used by the stems and/or low branches, or the extra 1 to 2 inches around the stem(s). Therefore, you can purchase less mulch than the calculations indicate. If you are using an organic mulch and buy more bags than you need, return the extras for a refund, if possible (check store policy). Do not store organic mulches, because they will rapidly decompose in the bag. Inorganic mulches, however, may be stored.

BENEFITS OF MULCHING

• Mulches can prevent loss of water from the soil by evaporation. Moisture moves by capillary action to the surface and evaporates if the soil is not covered by a mulch.

   

• Mulches suppress weeds when the mulch material itself is weed-free and applied deeply enough to prevent weed germination or to smother existing small weeds.

   

• A more uniform soil temperature can be maintained by mulching. The mulch acts as an insulator that keeps the soil cool under intense sunlight and warm during cold weather.

   

• Mulching will prevent crusting of the soil surface, thus improving absorption and percolation of water into the soil and, at the same time, reducing erosion.

   

• Organic materials used as a mulch can improve soil structure and tilth. As mulch decays, the material becomes topsoil. Decaying mulch may also add nutrients to the soil.

   

• Mulches also add to the beauty of the landscape by providing a cover of uniform color and interesting texture to the surface.

   

• Mulched plants will produce roots in the mulch that surrounds them. These roots are produced in addition to the roots that a plant produces in the soil. As a result, mulched plants have more roots than unmulched plants.

REFERENCES

Stinson, J. M., G. H. Brinen, D. B. McConnell and R. J. Black. 1990. "Evaluation of landscape mulches". Proc. Fla. Hort. Soc. 103:372-377.