What is Mulching?
Mulch is a layer of material applied on the top of your soil. Mulch maintains a more constant soil temperature, provides nutrients for your plants, and keeps your soil moist throughout the summer. Mulching will reduce weed germination and the amount of water needed for the plants. It also stimulates biological activity near the surface of the soil. The benefits go on and on…
- Best applied in the late spring. It can slow soil warming if applied too early in the spring when seeds are still germinating. Mulch is best applied to your beds after transplants have been placed in the soil and direct-seeded crops have emerged and grown partway to maturity.
- Also applied again in the late fall to help over-winter certain vegetables and herbs. If you want your plants to survive the winter, this is very important!
- Do not till the mulch into your garden soil immediately before planting in the spring because the decomposition will tie up nitrogen that plants need to grow.
- To prevent weeds, lay a thicker layer of mulch to prevent weed emergence.
- If you have a plentiful and continuous supply of mulch, consider sheet mulching. This involves laying down continuous layers of mulch throughout the year and never tilling the soil. The mulch continues to break down, creating a thick layer of rich soil.
Types of Mulch to Use
We suggest the following mulch options, with the best options listed first:
Apply a 1-2 inch layer of clippings around the base of plants. Green clippings are rich in nitrogen, which is slowly released to the plants. It is very important to use organic clippings that aren’t saturated with herbicides or synthetic fertilizers from the yard.
Leaves are a great mulch for the garden, especially if they are ground up or partially broken down. The ideal mulch would actually be ground up leaves and organic grass clippings, creating a great environment for biology and nutrient-release.
Apply a 1-2 inch layer underneath your maturing vegetable plants. You can leave straw mulch in place at the end of the growing season to protect the soil through the winter. Be sure the hay is “weed and seed free”, otherwise you’ll have a number of surprise crops in your garden the next year. Straw isn’t as good as green grass clippings, because it doesn’t have as much nitrogen in it (green materials are high in nitrogen, while brown materials are high in carbon).
Apply a 1-2 inch layer of low-salt compost around the base of maturing crops. Backyard compost is by far the best quality compost you can use. After applying a thin layer of compost, consider covering it with another type of mulch so the compost will stay moist and biologically active. Much like grass clippings, compost releases nutrients into the soil and maintains high biological life at the surface of the soil.
Many commercial growers use black or colored plastic to mulch their warm season crops. It’s great for heat-loving vegetables such as tomatoes, peppers, and eggplants, as well as for vine crops (cucumbers, summer and winter squash, pumpkins, watermelons, and cantaloupes). Plastic warms the soil allowing for earlier crop growth—typically 2-3 weeks earlier production with higher yields—but is too hot for all cold season crops. Only use plastic mulch if you’re only growing warm season crops. Plastic also retains soil water incredibly well, but doesn’t allow rainwater to permeate. To use plastic, lay the plastic over the entire bed, and pin or hold down the edges with rocks. Punch holes in the plastic for the plants, and sow or transplant seeds and seedlings into the holes. Do not use black mulch under shrubs and trees. If you use plastic mulch, save the plastic every year for re-use.
Types of Mulch Not to Use
Large pieces of organic matter such as wood chips can tie up nitrogen in your soil during decomposition. When they lie on the top of the soil, there usually aren’t an issue. However, wood chips inevitably work their way into the soil when the soil is tilled or moved during planting. The wood chips also tend to get in the way in future years when trying to amend the soil or plant.
Peat moss used as mulch tends to dry up and blow away. It does not hold water very well, and adds no nutrients to the soil. It is also significantly more expensive than other mulch options.
Manure (depending on the type) tends to be high in salts, so we do not suggest adding very much of it to your vegetable garden every year.