Every two to three years in the spring we perform a ritual at our house that is repeated at many other homes in our area – the spreading of the mulch. This has become such a tradition it should be noted on our calendars as Mulch Day! This year as I watched the truck dump a huge pile of mulch on our driveway I started thinking about why we do this. What is the purpose of mulch? Are there right and wrong ways to spread it?
There are many good reasons to mulch garden beds. Mulch helps retain moisture in the soil and control weeds. Organic mulch improves the soil as it breaks down, increasing aeration and drainage. It provides a buffer between tree trunks and lawn equipment thus reducing mower damage to tree bark. Finally, it gives a neat, well-cared-for appearance to our gardens.
Spreading mulch is a simple task, but there are right and wrong ways of doing it. Here are the correct steps to take:
1. Apply to a depth of 2 to 4 inches. Mulch that is too thickly applied will smother roots.
2. Use organic material such as wood chips, pine needles, chopped leaves or compost mixes.
3. Apply only as needed. Different materials decompose at different rates. If too much mulch is applied over time it can lead to excess moisture in the root zones that can cause rot and disease. Raking mulch can give a fresh appearance without the need for an additional layer.
4. Leave 2”-3” of space around the stems of perennials.
5. Do not mound mulch up against the base of a tree. These “volcanoes” are detrimental to the tree, but the damage occurs over time so the connection between the mulch hills and dying tree is not immediately apparent. Mulch piled up against the tree bark creates a dark, moist environment that promotes rot and invites disease and insects that destroy the tree bark.
Bark is meant to protect the tree trunk and it needs light and air to remain healthy. Mulch piles also produce heat that may kill the inner bark or phloem layer of young trees impeding the flow of nutrients in the tree.
Finally, mulch piles promote the development of secondary roots that can encircle the trunk and choke off the main roots. Applying mulch around the base of a tree is a good thing, but spread it only up to and not against the bark.
Mastering the do’s and don’ts of mulch is simple – use organic material and don’t spread too thickly or against stems or bark. If you follow these rules, your garden will remain healthy and beautiful for many years. Happy Mulch Day!
• Suzanne Thorne is a University of Illinois Extension Master Gardener for Kane County. Call the extension office at 630-584-6166 to learn more.