When choosing the right mulching material, consider what’s affordable, available, and appropriate for the task at hand. Are you mulching for weeds, warmth, aesthetic value, or water retention? Different mulches have different jobs throughout the garden.
Most mulches help your garden become a Climate Victory Garden because they protect life in the soil, encouraging the carbon capture that makes gardening part of the climate solution.
We encourage using organic mulches that persistently work to improve the health of the soil, that is, materials that are broken down by soil microbes to increase organic matter. Consider avoiding synthetic mulches like landscape fabric, because they do nothing for soil health and create more waste for the landfill.
Straw or hay
- Benefits: Best used to insulate perennials during the winter months.
- Drawbacks: Cheap hay is filled with weed seeds that can take over your garden.
- Bottom line: Buy the same quality of hay or straw that is used for feed and weeds shouldn’t be a problem.
- Benefits: Great for adding nutrients, particularly phosphorus, to the soil.
- Drawbacks: It can get “hot” enough to kill your plants when left in clumps more than one inch thick.
- Bottom line: Use thin layers of grass to add nutrients and avoid suffocating your plants.
- Benefits: Lightweight and easy to handle. It's also a great source of phosphorus.
- Drawbacks: Expensive and the high nutrient content makes it toxic to pets.
- Bottom line: Use it in the greenhouse for seedlings. The expense and potential hazard outweigh its benefit in the garden.
- Benefits: You can find nearly an endless supply in the fall. Ask your friends to save them too!
- Drawbacks: Whole, dry leaves can mat together and prevent water from reaching the soil.
- Bottom line: Leaves make amazing mulch if they are shredded by a mower or left to dry out and crumbled.
Gravel or pebbles
- Benefits: Perfect for plants that need drainage. Rocks also absorb heat during the day and release it during the night, which protects cold-sensitive plants.
- Drawbacks: Pebbles can be messy and make it hard to dig.
- Bottom line: Save the pebbles for your succulent garden or planters.
Wood chips or bark
- Benefits: Easy to get from your local utility company. They also slowly decompose so you won't have to replace as often.
- Drawbacks: High carbon content can steal nutrients from the soil surface. Mulches like wood chips, straw, and sawdust are high in carbon and low in nitrogen. When soil microbes eat the mulch, they pull all of the available nitrogen from the soil surface in order to break down the woody materials. This creates a localized nutrient deficiency around plant roots. Offset this by mixing in a high nitrogen fertilizer, such as blood meal or fish meal, when applying woody mulches.
- Bottom line: Save the bark for pathways and areas that see a lot of foot traffic.
Newspaper or cardboard
- Benefits: Abundant in today’s age of Amazon packages arriving almost daily. A great alternative to weed fabric.
- Drawbacks: Some inks and glues contain toxic chemicals.
- Bottom line: Most inks are soy based so they are safe for the garden. Avoid using glossy paper or boxes coated in colored inks.
- Benefits: Very inexpensive because it is a waste product.
- Drawbacks: Very acidic and messy.
- Bottom line: Only use sawdust around your acid-loving perennials, like blueberries.