The Fine Art of Mulching Trees
If you think mulching is merely a compulsion of those addicted to yard work, think again. Studies show that a mulched tree can grow double or even triple the rate of an unmulched tree. So not only will mulch add artistic flair to your landscape, it will help you develop a good root system and a generally healthy tree by:
- insulating soil
- retaining moisture
- blocking weeds
- keeping soil from compacting
- protecting against lawnmower damage
However, applying mulch incorrectly -like building a volcano of it around your tree trunk- creates moist conditions that can lead to rot or insect invasion. Unfortunately, mulch bags don’t come with lots of directions; but applying mulch properly is easy if you follow a few simple guidelines.
First, what kind of mulch should you use? There are two basic types of mulch: organic and inorganic. Organic mulches, derived from plant material, decompose to enrich and improve the soil. They typically contain both major and minor mineral elements essential for plant growth. Manure, sphagnum peat moss and pine needles are all examples of organic mulch. Leaves and composted yard waste while good for soil improvement don't score high in the longevity category. The most popular mulch for both weed control and longevity is shredded hardwood, chip, or chunk bark. Although finely ground chips are popular, look for a mulch that has a mix of large, medium, and small wood chips. This allows for better water and air movement to the soil and tree roots.
Stone, pebbles, and plastic are types of inorganic or fabricated mulches. These are utilized mainly for color and texture changes. Like all inorganic mulches, they offer no value as breakdown products in the soil.
A relatively new inorganic product is geotextiles or landscape fabrics. These fabrics have replaced black polyethylene film as an effective weed barrier to be used under more decorative products such as stones or bark.
You'll also want to consider mulch cost and longevity. Visit local garden stores and nurseries to compare prices. If you need lots of mulch, check into buying it by the truckload. Some municipalities and utility companies even give away wood chips for free. If you opt for fresh, free wood chips, make sure to let them sit for three to six months prior to using around plants. This gives it the time to "cook out" unwanted pathogens and weed seeds. To save money, some people use more attractive and expensive mulches in high visibility areas like front yards and less expensive mulches in lower visibility sites like backyards.
Longevity refers to the length of time required for a mulch to break down. Mulches that break down slowly improve the soil slowly, and don’t need to be reapplied as frequently. In contrast, mulches that break down more quickly provide better soil benefits, but need to be applied more often. For sites with poor soil, choosing a mulch with shorter longevity may be the best option.
Once you've determined what kind of mulch to use, the next consideration is when to mulch. In Ohio, the best time to put down mulch is in the spring after the soil has warmed and begun to dry from winter rains and snow. A second application may be needed in autumn after the first frost to reduce heaving which breaks tree roots and leads to winter injury.
How deep should mulch be? The ideal depth is two to three inches. If you're using shredded hardwood mulch, lay it about four inches deep to allow for settling. Mulch laid too thickly prevents drying and leads to water-logged soil, particularly during wet seasons. Speaking of water, some people like watering down new mulch to help it stay in place, although this is not really necessary.
A common mulching myth is the belief that old mulch should be removed before adding new. Not true. Simply refresh old mulch by fluffing it up and adding enough new mulch to bring the depth back up to two inches.
Trees need water and nutrients from the soil to survive. Proper mulching helps ensure your trees have what they need to live long, healthy lives and helps beautify your yard at the same time.