The main reasons backyard gardeners use mulch is for weed suppression in warm weather, soil insulation during colder temperatures and moisture retention year-round. These factors, as well as cost and how it looks in your flower bed, are points to consider when picking the mulch you will use in your garden.
The following mulches are some of the most commonly used by gardeners, and the pros and cons associated with each type:
Pine needle mulch (pine straw)
This option is widely used for a variety of reasons. It is one of the least expensive options available on the market. If you are fortunate enough to have pine trees on your property, this is a great free option. As a bonus, raking provides a good physical workout. Applying a 2- to 3-inch layer of pine needles will help suppress weeds as well as keep the soil warm and moist.
Pine straw decomposes slowly, so replenishing it should only be necessary once a year. However, many gardeners lay down mulch in spring and again in fall. Since pine straw is acidic, when it does decompose, it feeds acid-loving plants such as azaleas, blueberries, boxwoods and hydrangeas.
Pine bark mulch
Pine bark mulch is one of the most common mulches used in beds, largely because it is the most visually appealing. It also does a good job of keeping soil warm and retaining moisture, as well as suppressing weeds. This is a moderately priced option, just slightly more expensive than pine straw.
Pine bark mulch breaks down fairly quickly, which is a pro because it adds nutrients to the soil, but a con because you have to replace it a little more regularly. Pine bark mulch also has the potential to draw bugs, especially spider mites. It is not very good on slopes or areas where rain water can easily wash it away.
Straw and hay
Straw and hay are not considered as aesthetically pleasing as other mulches, but they provide excellent insulation in summer and winter. Straw, in particular, is a favorite choice for winter mulching, as the straw needles are hollow, providing dead air space, which is ultimately the perfect insulator. They are the perfect mulch when seeding a new lawn.
Hay, unfortunately, has the con of often being riddled with weed seeds, which will inadvertently introduce weeds into the garden that weren’t there before. Unless available free of charge, it is a slightly higher priced option than pine needles or bark.
Leaves are a wonderful free mulch; however, they need to be shredded before use. They are very good when used over vegetable beds in fall, as they will decompose throughout the winter, which will add nutrients to the soil.
They are commonly used around trees and bushes and in less formal settings. The leaves also attract earthworms, which are beneficial to soil health, help with soil aeration and compaction, and help with nematode control.
Leaves over time have the tendency to compact together and form a mat, inhibiting air and water flow, especially if they have not been shredded. Leaves can easily be raked and "fluffed up" when they become matted.
Grass clippings come with a lot of cons. They are high in water content, so they decompose very quickly. This unfortunately makes them very slimy, and it produces a foul odor.
They have a tendency to mat down, inhibiting air flow. If clippings have been treated with herbicides, pesticides or weed killer, they can be harmful to your plants. Grass clippings are best left on the lawn to return nutrients to the soil. The pro: They’re free.
There are a variety of inorganic mulches available. Rocks and gravel, although they create a very clean look, can be expensive. They also absorb heat from the sun which can cause the area to become hot and dry. The use of these materials is best in beds without plants or those that are drought resistant.
Rock and gravel mulches are generally used together with plastic or fabric landscaping sheeting, adding to the cost. Plastic sheeting does not allow proper air flow or for water to penetrate through to the soil. Although fabric sheeting is better for allowing air and water to pass through, weeds can also penetrate through the fabric.
Rubber mulch is usually made from ground, recycled tires and dyed to compliment or stand out in the garden. It is good at suppressing weeds and for maintaining moisture in the soil. There are still studies being performed to determine the toxicity of rubber mulches. It does not break down and can remain in the soil for long periods of time. It is one of the more expensive mulch choices.
With any mulch, make sure to keep it a few inches from the base of plants and trees to avoid damage from moisture or cause mold to form. Until next week, happy gardening.
— Irland, a member of the Limestone County Master Gardeners, can be reached at email@example.com. Visit https://mg.aces.edu/limestone for more information on the Limestone County Master Gardeners.