Maureen Sexsmith-West
ISA Certified Arborist, PR4600A
The true purpose of mulch is to simulate nature, retain moisture and to insulate roots against winter frost.
Mulching is a great thing for your plants, especially newly planted trees. Keep some of these key points in mind when selecting a product.
ORGANIC MULCH is the best thing going for plants, after all, it is the leaf litter and decomposing materials that create the rich soil on forest floors. There are bacteria, fungi and insects that all work to break down this material. Our tendency in the urban landscape is to rake up every last leaf or needle to create a clean look. We take all the organic materials your tree needs to the landfill and end up buying mulch. The mulch initially has to steal the nitrates and organic elements from your tree’s root zone. When applying mulch apply a light sprinkling of fertilizer (like the type used on spring lawns) first and then water it in.
Turn your mulch beds annually (in late fall) and replenish with fresh chips to maintain a level of 3-4” ever other year. This makes your mulch a much less attractive location for over-wintering insects and disturbs seeds that blow in.
HARD LANDSCAPE PRODUCTSsuch as gravel and brick absorb and hold heat. Try walking on barefoot on pavement and then on grass on a hot day – notice the difference in temperature? In direct sun you create a stress for your plant. Gravel increases soil temperatures. To help counter act the gravel’s ability to hold heat, be sure to water more frequently to help manage soil temperature. It also compacts the soil.
A condition which often results in gravel beds is “scorch”. This occurs when the sun’s rays are reflected from the rock (particularly white or light coloured) to the underside of the plant’s leaves and the lower branches and trunk (similar to sunburn). When selecting a gravel product – use something that is darker in color.
Key Points
Landscape fabrics don’t prevent weeds. Weeds germinate from seeds, and soil, that blow into the mulch bed. Weeds and volunteer plants should pull up easily in 3-4 inches of mulch.
Mulch beds should be NO MORE than 4 inches deep – roots need to have oxygen available at a specific depth.
Organic products usually need to be complimented initially with fertilizers to prevent stealing nitrates from the soil
DO NOT pile mulch against the trunk of your tree. Allow at least 2 inches of free space to allow for growth and air exchange. Gravel can cause lesions on the trunk or actually become embedded in the bark. This irritation is an open door to fungal and bacterial problems at a point where injuries can result in failures. Inspect annually and make corrections as needed.
When possible, mulch products should be made up of the same wood type as tree – evergreens for evergreens and deciduous for deciduous.
NEVER USE PLASTIC! It does not allow for oxygen and moisture exchange and can actually make your soil toxic.
Plants need to be watered deeply and regularly to remain healthy. As milder temperatures persist this fall, be sure to give your trees an extra drink before freeze up.
