Sally Scalera

Brevard County Horticulture Extension Agent
3695 Lake Drive -- Cocoa FL 32926 -- 321-633-1702

Mulch

April 14, 2007

Now that spring is here, it is time to get out into the landscape and start having some fun again. Usually when spring hits we are full of ideas of things to do, but one of the most important tasks that we can do to protect and help our plants is to mulch them. here are a lot of benefits to mulching plants and it is easy to do.

Just to give you an idea of how important mulching is, here are some of the benefits. Mulch can prevent water loss from the soil by evaporation. Moisture moves by capillary action to the surface and evaporates if the soil is not covered by mulch. When you take into consideration that our typical soil is sand and the fact that we are still in a drought, it just shows how important mulch is to the plants. Another benefit of mulching is that it suppresses weeds when it is applied three to four inches deep. A thick layer of mulch shades and covers the soil so that any weed seeds on the surface won’t germinate.

Mulch is also great because it helps moderate the soil temperature. This is very important throughout most of the summer and during our cold spells in the winter. If you have ever tried to walk on the beach on a summer afternoon you will understand how hot sand can get. By placing mulch over the soil surface and shading it, the soil does not heat up. The roots of the plants are able to grow continuously because of the shading. The opposite is true in winter since mulch keeps the soil warmer so, it is very common to have some plants killed to the ground like bananas or ginger plants, but when spring comes the plant grows back from the roots.

Mulching plants can also prevent crusting of the soil surface, thus improving absorption and percolation of water into the soil. An additional benefit is that mulch reduces soil erosion. The most important reason for using mulch for me though, is that organic materials used as a mulch can improve the soil by adding organic matter to our sandy soil. Organic matter is food for the soil microbes that supply nutrients to the plants, and it can improve the soil structure. Organic matter can increase the water holding capacity of the soil which is very helpful during a drought.

For those of you growing vegetables, mulch is great because it can help prevent soil from splashing up to the leaves that can spread diseases. Bacterial leaf spot of tomatoes is a common disease and it gets into the lower leaves of a tomato plant by the movement of the soil splashing up. If there is mulch over the soil there will be no splashing of the soil and bacteria so, no disease!

Now let’s look at some of the different types of materials that can be used for mulch. Pine bark nuggets, wood chips like golden mulch from our landfills, grass clippings, brown leaves, aged pine needles and compost can all be used as mulch. Pine bark nuggets are great though their color is a darker brown. They work well under trees, shrubs and perennials and they are slower to break down so, they do last longer then some of the other materials.

Wood chips, like the golden mulch that is available from our landfills, are also great to use under trees, shrubs and perennials. Because they are also larger pieces they tend to last longer before breaking down so, they don’t need to be replenished as often.

Grass clippings are good to use too, but it is best to let them dry out some before spreading them under plants like vegetables, annuals, etc. With grass clippings you will also get increased earthworm activity which is another added benefit! Grass clippings are also great to let fall when you are mowing since they add nutrients and organic matter to the turf so you may not have any grass clippings to use.

Brown leaves that you rake up (like the oak leaves and leaves of deciduous trees) are good to use as mulch. Oak leaves are fine to use whole, which just means they will be slower to break down, but they still make a great mulch. I often hear people say that oak leaves and pine needles make the soil acidic but that is not the case. I asked one of our specialists in Gainesville who is a soil scientist about that and he said that no mulch on the surface of the soil changes the pH below ground. So, if you have oak leaves and you were putting them out for the yard trash truck to pick up, you can now start saving them for your plants!

Pine needles are great to use also, but it is best to pile them up and let them age for a little while before putting them under your plants. You can either use them whole or chop them up into smaller pieces. If you chop the brown leaves and pine needles up before mulching with them you will find that they break down faster. This is actually a good thing, but would mean that you would have to reapply mulch more often. Anyone who has a compost pile can use the humus (the end product of composting) as mulch. This will also increase earthworm activity just like using grass clippings, and chopped up brown leaves and pine needles.

Mulching is pretty simple with just two rules to follow. Rule number one is to keep the mulch about three to four inches thick over the roots of plants. The second rule is to keep the mulch a couple inches away from the trunks or stems of plants. The one big exception to this rule is to keep the mulch 6-12 inches away from the trunks of citrus trees, but otherwise, it is still beneficial to mulch citrus trees too. So, go check your plants and see if they could use some more mulch!