Using Mulch for Plant Health

In the yearly cycle of things, it is time to reapply mulch to the plants in your landscape, and contrary to popular belief, this isn’t done just for appearance sake. Mulch plays a key role in the health and life span of nearly every plant you own.

The reason for applying mulch over the root zones of plants and trees in the fall and then again in the summer is to guard against rapid temperature changes and moisture loss. We can’t keep plants warm or cool with mulch, but we can use mulch to prevent quick changes in temperature or moisture that can weaken plants. Mulch imitates the natural conditions of organic matter breakdown found in the wood and provides a layer of insulation for the root zone. It protects while maintaining air for the roots and works much like a down-filled jacket. Mulch applied in the fall allows the root system to freeze gradually, and in the spring, it slows warming and growth until the threat of heavy freezes is past. Mulch re-applied during the beginning days of summer protects roots from extreme drying and rapid upper level soil temperature changes.

Mulching is one of the best things you can do for your plants, but there are a couple of commonly made mistakes that can defeat the purpose. First, many people apply too much mulch. This can cause problems. A thick layer can shed water and it cuts off air circulation to the root zone causing suffocation. In addition, too much mulch can trap excess moisture and help disease or decay get started. It is also a mistake to take mulch right up to the trunks of your trees and shrubs. When this is done, it provides a cozy route for rodents to follow in the search for a food source and visual protection while eating.

The other mistake people make when applying mulch is to do so at the wrong times of the year. In the fall, mulch should by applied no more than three inches deep to regulate freezing and thawing. In the spring, you should fluff up what is left and add only enough to bring the depth back to a total of 3 inches. Waiting allows the sunlight to get through to warm the soil for spring growth. Then re-apply mulch in early to mid June. Even then it’s not necessary to remove old mulch and apply new. Simply take the total depth up to 3 inches maximum, placing fresh mulch on the surface for a neater and fresher look.

The exception to these guidelines is roses. Roses need to be completely hilled up to 18 inches during late fall, and in the spring the old mulch must be removed, used elsewhere, and fresh mulch applied to help avoid black spot carry over and other diseases. Check with your nursery or garden center for if you need more specifics on this practice.

One final thought --- when you’re choosing a mulching material, look for fibrous or course materials that won’t pack down tightly. I like shredded cypress in permanent beds and pine bark of different sizes in beds that will be re-worked. Also consider using bark, shredded or chunk, even shredded and colored second use wood. The more actual wood used, the faster the mulch will break down from bacterial action, so add a little more nitrogen fertilizer to help modify the process. Check withy our garden center for specifics.

Now is the time to apply mulch to protect your plants from harsh summer temperatures and rapid drying. So get out there and do something great for your landscape.