mulch purpose.


Hi –  I was wondering what is the purpose of using mulch around the trees? i don’t usually put it around but some of my neighbours do. Thanks a lot.


A very good question, and not one often asked. Mulch is usually composed of organic material, though currently, there are a number of non organic materials used for some of the same purposes.

The organic materials can range from chipped, block or shredded bark (usually from evergreen trees), to coco bean shells, decaying leaves, straw or even already decomposed organic material we generally call compost. These materials are used for several purposes: enriching tired soil (compost is best for this), maintaining moisture for existing plants, weed suppression, and for many people, it keeps beds looking tidy and cohesive.

Often, especially in vegetable gardens, where tidy and cohesiveness is not necessarily a priority, but weed suppression is, layers of newspaper or cardboard between rows of crops are used for this purpose, and is sometimes called a mulch.

The non organic materials that have been showing up in the last number of years include recycled rubber (from tires) mats, and even chipped rubber that mimics the look of mulch. Master Gardeners rarely recommend the non organic type for any garden bed or tree planting.

We do recommend compost for many situations; adding to prepared holes dug for plants, improving the moisture retention of soil, improving the organic composition of soil that has been over used, and added to pots to improve drainage.

We often recommend shredded bark as a mulch around trees or in beds, to help with moisture retention and weed suppression. We usually recommend applying mulch to a depth of 10 to 15 cm (4 to 6 inches) for best results. When putting around a plant or tree, be sure the mulch does not touch the branches or trunk, as the retained moisture at that location could encourage fungal growth.

Leaves from trees, rather than raked into compost bags, can be used as winter mulch. They, along with purchased straw, are used to protect plants from the heaving that can happen during freeze/thaw cycles in the winter. Store the bale of straw or bags of leaves until the soil in the beds freeze, then rake the mulch over the beds for the winter. They then can be added to the compost bin in the spring to decompose further, and becoming the useful compost.

Most people, Master Gardeners included have found coco mulch clumps together, especially after rain and can start the cycle of fungal growth.