Correct Mulching Techniques & Services
Mulches are materials placed over the soil surface to maintain moisture and improve soil conditions. Mulching is one of the most beneficial things a home owner can do for the health of a tree. Mulch can reduce water loss from the soil, minimize weed competition, and improve soil structure. Properly applied, mulch can give landscapes a handsome, well-groomed appearance. Mulch must be applied properly; if it is to do its job.
- Helps to maintain soil moisture. Evaporation is reduced, and the need for watering can be minimized.
- Helps to control weeds. A 50-100mm layer of mulch will reduce the germination and growth of weeds.
- Serves as nature’s insulating blanket. Mulch keeps soils warmer in the winter and cooler in the summer.
- Many types of mulch can improve soil aeration, structure (aggregation of soil particles), and drainage over time.
- Some mulch can improve soil fertility.
- A layer of mulch can inhibit certain plant diseases.
- Mulching around trees helps facilitate maintenance and can reduce the likelihood of damage to the bark and stem tissues from “brush cutters” or the dreaded “lawn mower blight.”
- Mulch can give planting beds a uniform, well-cared-for look.
Trees growing in a natural forest environment usually have their roots anchored in a rich, well aerated soil full of essential nutrients. The soil is blanketed by leaves and organic materials that replenish nutrients and provide an optimal environment for root growth and mineral uptake.
Urban landscapes, however, are typically a much harsher environment with poor soils, little organic matter, and large fluctuations in temperature and moisture. Applying a 50-100mm layer of organic mulch can mimic a more natural environment and improve plant health.
The root system of a tree is not a mirror image of the top. The roots of most trees can extend out a significant distance from the tree trunk.
Although the guideline for many maintenance practices is the drip line—the outermost extension of the canopy—the roots can grow many times that distance.
In addition most of the fine, absorbing roots are located within 30cm of the soil surface. These roots, which are essential for taking up water and minerals, require oxygen to survive.
A thin layer of mulch, applied as broadly as practical, can improve the soil structure, oxygen levels, temperature, and moisture availability where these roots grow.
Types of Mulch
Mulches are available commercially in many forms. The two major types of mulch are inorganic and organic.
Inorganic mulches include various types of stone, lava rock, pulverized rubber, geotextile fabrics, and other materials. Inorganic mulches do not decompose and do not need to be replenished often. On the other hand, they do not improve soil structure, add organic materials, or provide nutrients.
Organic mulches include wood chips, pine needles, hardwood and softwood bark, cocoa hulls, leaves, compost mixes, and a variety of other products derived from plants. Organic mulches decompose in the landscape at different rates depending on the material and climate. Those that decompose faster must be replenished more often.
As the decomposition process improves soil quality and fertility. Organic mulches, such as Forest Mulch, will help to achieve healthy plant growth.
Not Too Much!
As beneficial as mulch is, too much can be harmful. The generally recommended mulching depth is 50-100mm.
Unfotunately, many landscapes are falling victim to a plague of over mulching. A new term, “mulch volcanoes,” has emerged to describe mulch that has been piled up around the base of trees.
Most organic mulch must be replenished, but the rate of decomposition varies. Some mulch, such as cypress mulch, can remain intact for many years.
Top dressing with new mulch annually (often for the sake of refreshing the colour) creates a build-up to depths that can be unhealthy. Deep mulch can be effective in suppressing weeds and reducing maintenance, but it often causes additional problems.
Problems Associated with Improper Mulching
- Deep mulch can lead to excess moisture in the root zone, which can stress the plant and cause root rot.
- Piling mulch against the trunk or stems of plants can stress stem tissues and may lead to insect and disease problems.
- Some mulch, especially those containing cut grass, can affect soil pH. Continued use of certain mulch over long periods can lead to micronutrient deficiencies or toxicities. Mulch piled high against the trunks of young trees may create habitats for rodents that chew the bark and can girdle the trees.
- Thick blankets of fine mulch can become matted and may prevent the penetration of water and air. In addition, a thick layer of fine mulch can become like potting soil and may support weed growth.
- Anaerobic or “sour” mulch may give off pungent odours and the alcohols and organic acids that build up may be toxic to young plants
It is clear that the choice of mulch and the method of application can be important to the health of landscape plants. The following are some guidelines to use when applying mulch.
- Inspect plants and soil in the area to be mulched. Determine whether drainage is adequate. Determine whether there are plants that may be affected by the choice of mulch. Most commonly available mulches work well in most landscapes.
- If mulch is already present, check the depth. Do not add mulch if there is a sufficient layer in place (no deeper than 100mm). Rake the old mulch to break up any matted layers and to refresh the appearance.
- If mulch is piled against the stems or tree trunks, pull it back several inches so that the base of the trunk and the root crown are exposed.
- Organic mulches are preferred to inorganic materials due to their soil-enhancing properties. If organic mulch is used, it should be well aerated and, preferably, composted. Avoid sour-smelling mulch.
- Forest Mulch makes good mulch, as it contains a blend of leaves, bark and wood. Avoid using non-composted mulch that has been piled deeply without exposure to oxygen.
- For well-drained sites, apply a 50-100mm layer of mulch. If there are drainage problems, a thinner layer should be used.
- Avoid placing mulch against the tree trunks. Place mulch out to the tree’s drip line or beyond.
Remember: If the tree had a say in the matter, its entire root system (which usually extends well beyond the drip line) would be mulched.