Mulching Your Flower Beds

Tips and suggestions on the best mulch to use for your flower beds, the benefits of mulching and instructions on how to apply mulch.

What is Mulch?

There are two kinds of mulch, organic and inorganic. Organic mulch decomposes, whereas inorganic mulch does not. Examples of organic mulch include grass clippings, straw, shredded bark, newspaper (shredded or entire), wood chips, or cocoa bean hulls. Inorganic mulch refers to plastic sheeting, gravel, or landscape fabric.

Benefits of Mulching Flower Beds

Mulch is used to keep the soil moist and reduce the amount of water that evaporates from the soil. Mulching flower beds prevents soil from compacting. If soil is compacted, then water cannot percolate into the soil for plants to use. Mulch also prevent weeds from growing, and helps to moderate soil temperatures.

What Kind Should I Use?

Organic mulches are preferred to inorganic ones for several reasons. As organic mulch decomposes, it enriches the soil with organic matter and nutrients. A soil rich in organic matter also provides a habitat for earthworms, which in turn, aerate the soil and aid in bacterial decomposition. Organic mulches are better at keeping the soil cool during hot summers and warmer during the cooler weather in the fall.

The preferred mulch for flower beds is triple shredded hardwood or pine bark mulch that has been aged at least one year. Mulch that has been aged is partially decomposed and contributes organic matter and nutrients to the soil more quickly. Wood chips are another option that usually works well for flower beds, although they are typically not aged.

Finer grade mulch such as triple shredded bark is better than a coarse grade of mulch such as large chunks of bark. It is easier to spread around the flowers, and a thinner layer of mulch is needed to cover the underlying soil.

In addition, triple shredded bark mulch is more naturalistic looking and provides a neutral backdrop for your flowers, instead of competing with them. Triple shredded bark mulch is sometimes dyed red or shades of brown, although the mulch tends to look artificial when compared to natural color mulch.



Grass clippings, straw, cocoa bean hulls, and shredded newspaper are other options; however, they are not as effective as shredded bark mulch. Grass clippings have a tendency to clump or mat so that water cannot percolate into the soil, and are less aesthetically pleasing.

Straw is impractical for flower beds because it decomposes rapidly necessitating a very thick layer of mulch, which may dwarf flowers. Although they are attractive, cocoa bean hulls do not decompose as well as shredded bark mulch. Shredded newspaper is not very attractive and is better used for other applications such as seeding a lawn where the grass will obscure the newspaper shreds.

Mulch is available at most garden centers or large landscape nurseries and is sold by the cubic foot. For example, a 20 x 10 foot flower bed with a 4 inch layer of mulch would require about 67 cubic feet (CF) of mulch. Mulch is sold in bags or in bulk.

How to Apply Mulch

The mulch layer should be a minimum of 3 to 4 inches to block sunlight and prevent weeds from germinating. Mulch settles as it decomposes, so it is necessary to apply about an inch more than you want the final thickness of the mulch layer to be. If you need a 4-inch layer of mulch, then apply 5 inches to start. Use a 4 to 5 inch mulch layer in sandy soils and a 3 inch layer in loam soils that retain water well.

To prevent weed seeds from germinating in your flower bed, apply mulch right after the soil thaws, usually in late spring but before the warm season begins. Before applying mulch remove all weed plants from the soil. Spread the mulch around the entire flower bed leaving a few inches around the base of the plants. Good air circulation is important in preventing mold from developing.

As mulch decomposes, top off the mulch layer. Typically you will need to do this once a year. Because the soil in mulched beds is slower to warm up in the spring, add more mulch after the soil warms up.

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