Once the weather cools down in the fall and there’s less mowing to be done, it’s time to think about mulching around plants, shrubs and trees to prepare them for winter. Although throwing some wood chips or pine straw on your planting beds may seem like a no-brainer, getting it wrong could actually harm your trees and plants. Avoiding these six common mistakes will keep your plantings healthy and help support your soil as well.

1. The Wrong Mulch

There are many types of mulch, including organic mulches like wood bark, wood chips and pine straw as well as inorganics like rock, stone and rubber. Rock and stone absorb heat, which is fine in the winter but will cause heat stress for plants during hot, dry weather. Rubber is great underneath a child’s playset, but it can leach chemicals into the soil, which may be toxic to plants. Reserve inorganics for walkways, playgrounds and other areas away from trees and plantings.

2. Too Little Mulch

Skimping to save money or time will minimize or cancel out the benefits of mulching. Three inches of mulch is ideal. If you get it right, the mulch helps retain moisture and regulate the temperature of your soil, protecting your plants through winter. It will also help with soil aeration, fertility and drainage and, of course, weed control.

3. Too Much Mulch

Using more than three inches of mulch can choke plant roots, blocking necessary air and water from reaching the soil. Worst of all, mulch piled too thick creates the perfect habitat for rodents and insects to take up residence—and nobody wants that.

4. Volcano Mulching

Layering mulch up onto the base of plants and trees will do more harm than good. Even large mature trees can be affected, potentially killing them by rotting the bark and exposing them to disease and insects. Smaller shrubs and plants are susceptible to rot as well, so keep the mulch two or three inches from the base of plants and trees to give them breathing room.

5. Uncomposted Mulch

When you buy mulch from a nursery or home store, you’re buying mulch that has been composted, which means that it has been dried and aged. When fresh wood chips first begin to break down, they rob nitrogen from the soil that your plants need to thrive. Getting fresh wood chips from a municipality can be a great way to save money, but compost it first. Simply let it sit in a pile for several months to a year, turning it with a shovel occasionally, before using it as mulch for your plants.

6. Layering Mulch

Layering mulch on existing beds year after year can cause the older material to compact and choke your soil and plants. Also, as time passes, it’s difficult to tell how much mulch is already on the ground. At least once a year, rake through any existing mulch down to the soil. This will break up compacted mulch, allowing water and air through. It will also save you money and effort—if you already have a couple inches of mulch on the ground, you only need to add one more inch.