Most people think of mulch when they want to manicure their landscaping. But it can also be the best (or worst) thing you can do for the health of your trees. Mulch has the ability to reduce water loss and improve soil structure. If applied incorrectly, it can actually starve and kill your trees.
Use the right type of mulch
Unlike trees naturally growing in forests, urban trees don’t benefit from well aerated and nutrient-rich soil. To mimic the natural protection and nutrient delivery of organic material on the forest floor, use mulch to improve plant health.
There are various types of mulch from rocks to wood chips to rubber. The two main types are organic and inorganic. Inorganic mulches like stone and fabric are low-maintenance and can offer some protection, but they don’t decompose or add nutrients.
Most arborists prefer organic mulches that break down quickly, offer protection, provide nutrients. Organic mulches are materials like pine needles, compost, and untreated wood chips. They type of mulch you use will depend on the quality of the soil, the climate, and the type of plant.
Do a little research on your soil type (e.g. acidic, clay-heavy) and the species of tree or plant you are trying to serve before choosing a mulch. If you’re worried about the choice, a professional arborist can help you decide.
Don’t use too much mulch
While it may be aesthetically pleasing, creating a mulch mountain around your tree won’t do it any favors. A mulch depth of 2-4 inches is ideal for avoiding root rot caused by excess moisture, the burrowing a feeding of rodents, and weed growth.
Pay attention to how fast your mulch is decomposing (it’s supposed to!) and don’t replace it before most of it is gone. Avoid piling up new layers each season.
Proper mulching techniques
- Use a 2-4 inch layer of organic mulch if the area is well-drained. If the soil has a slow drain, use a thinner layer.
- Add mulch all the way to the drip line of the tree (where it drips water after a rain) or extend a little bit beyond.
- Don’t pile mulch against tree trunks.
- Break up matted layers of existing mulch before adding more.
- If you’re worried about the coloring of your mulch, use an organic, vegetable-based mulch dye to improve the color. Buy it at your local hardware store or hire a landscape service to help.
- Avoid “sour” smelling mulch. It’s usually acidic and can harm some plants.
The Bottom Line
Take the time to investigate the drainage level of your soil and the types of mulch you tree species like best. Once you’ve determined the best material and method, follow our mulching techniques to ensure a long life for your trees. And if you’re worried you’ll mess it up, call a professional arborist or landscaper to assist you.