How Much Mulch?

Mulch serves a variety of valuable purposes but many people apply it improperly. Those huge mounds of mulch which you often see in landscapes could be a waste of money and injurious to the plants.

Mulch is very beneficial in that it helps the soil retain moisture, slows down the rate at which the soil freezes and thaws, helps control weeds, and provides a non-mowing strip so you don't have to mow right up next to the tree or other plants.

Fresh, fluffy, shredded mulch only needs to be applied about three or four inches thick which will then settle to a two-inch depth. Chunk bark should be laid only two inches deep because it will not settle as much.

Before applying mulch, the sod should be removed taking with it about one inch of soil. If the mulch is laid directly on top of grass, the blades will eventually grow back up through the mulch.

Mulch usually comes in three cubic feet bags which can cover an area about 18 square feet at a two inch depth, ample enough for a six by three foot shrub bed. Applied at a three to four inch depth it will only cover an area about ten square feet.

Once mulch is applied, I prefer to water it to help keep it in place but it is not critical for the plants.

Mulch should be refreshed once or twice a year as needed. Notice I said refreshed and not removed, which is an expensive practice that confuses many well-intentioned folks. Mulch does decompose over time, but it does not get old like motor oil and need to be changed regularly. To refresh mulch gently fluff up the old and then add enough new mulch to bring it up to the two to three inch depth for shredded bark to settle back to two inches, and again, only two inches for chunk bark. Sometimes you are only going to dust some new on the surface to make it look fresh.

You can also use peat moss as a mulch which can look particularly attractive in the annual flower beds, but it needs to be watered at least three times in order for the water to flow through it. Another consideration in selecting mulch is that bark fiber does not break down as quickly wood fiber and can make a more ideal mulch.

The faster mulch decomposes the more nitrogen it uses from the soil. Therefore, you may need to apply nitrogen at the time mulch is added. On pound actual nitrogen per 1000 square feet per year is the recommended application rate. Nitrogen available in fertilizer with a 10-10-10 analysis of nitrogen, phosphorous, and potassium works well. It is best to apply half the amount in the spring and the remaining half in the fall.
One practice I do not recommend is laying plastic over the soil before applying mulch. This causes the soil to retain too much moisture in the spring and too little is available in the summer.

Perennials, shrub beds, and evergreens that adjoin each other should be mulched all together for your mowing convenience. Shade trees only need to be mulched in an area the size of the original hoe on up to 4 or 5 feet total width. You do not need to increase that size as the plant gets older, but you may want to for aesthetic purposes. I don't like to use woody mulch on annual beds because it makes it difficult to plant new seedlings, but I do use peat moss which is easier to work with.

Mulch can do wonders for your landscape. If applied properly you'll save not only your plants but your money as well.