Best Mulch for Vegetable Gardens

The best mulch for vegetable beds is one that breaks down within a season or two and feeds the soil: straw, shredded leaves, grass clippings or compost. Wood chips and bark are better for paths and around perennials, where you won’t be digging every year.

Mulch keeps soil moist, smothers weed seedlings, evens out soil temperature and keeps soil from splashing onto leaves, which spreads disease. Once you have chosen a material, the Mulch Calculator tells you how much to buy.

Vegetable mulches compared

Mulch	Depth	Good for	Watch out for
Straw	3–4 in	Tomatoes, peppers, squash, potatoes	Buy straw, not hay, which is full of seeds
Shredded leaves	2–3 in	Almost everything; free in fall	Whole leaves mat down; shred them first
Grass clippings	1–2 in, thin layers	Between rows and around established plants	Thick layers turn slimy; avoid lawns treated with weed killer
Compost	1–2 in	Beds of greens and young plants	Feeds plants but weeds can root in it
Wood chips or bark	3–4 in	Paths, berries, perennial herbs	Hard to work around when sowing small seeds

Straw

Straw is the classic vegetable mulch. It is light, cheap by the bale and easy to spread around plants. It reflects light, keeps fruit off the soil and breaks down by the end of the season.

Make sure you buy straw, the dried stems of grain crops, and not hay, which includes grass seed heads and can plant a lawn in your beds. Ask the seller whether the straw is from fields sprayed with persistent herbicides; some residues survive for years and damage tomatoes, beans and peppers.

Shredded leaves

Fall leaves are free and make excellent mulch once shredded. Run a mower over a pile, or use a leaf vacuum with a shredder. Whole leaves form a wet mat that sheds water; shredded leaves let water through and break down into rich soil by the following year.

Store bags of shredded leaves over winter and use them in spring and summer.

Grass clippings

Clippings are rich in nitrogen and break down fast. Spread them in thin layers of an inch or so and let each layer dry before adding more; a thick wet layer heats up, smells and sheds water. Don’t use clippings from lawns treated with weed killers.

Compost

A layer of compost on the surface does double duty: it holds moisture like any mulch and feeds the soil as worms pull it in. It suits beds of lettuce, spinach and other greens planted close together, where a coarse mulch would get in the way. Weed seeds blowing in can sprout in it, so pull them while they are small.

Wood chips and bark

Wood chips last a long time, which is a drawback in beds you replant each season but an advantage on paths. Use them on walkways between raised beds, around fruit bushes and in perennial herb beds. Tree services often give arborist chips away for free.

Wood chips on the surface don’t steal nitrogen from plants in any meaningful way. The problem comes from mixing them into the soil, so keep them on top.

When to mulch

• Warm-season crops (tomatoes, peppers, squash, cucumbers): wait until the soil has warmed in late spring, about when nights stay above 50°F. Mulching cold soil keeps it cold.
• Cool-season crops (lettuce, peas, spinach, brassicas): mulch soon after planting to keep soil cool and moist as days warm up.
• Seeds: let seedlings get a few inches tall before mulching around them.
• Fall: a layer of leaves or straw over empty beds protects the soil through winter.

How to mulch

1. Weed the bed first. Mulch stops new weeds; it won’t kill established ones.
2. Water the soil thoroughly.
3. Spread mulch to the depth in the table, keeping it an inch or two away from stems.
4. Top up during the season as it breaks down.

Plastic mulch

Black plastic warms the soil and stops weeds completely. Commercial growers use it for melons, peppers and tomatoes in cool regions. It needs drip irrigation underneath, adds plastic waste and doesn’t improve the soil, so most home gardeners use it only to warm beds for a week or two before planting.

How much mulch do I need?

Multiply the area in square feet by the depth in inches and divide by 12 to get cubic feet. A 4×8 ft raised bed covered 3 inches deep takes 8 cubic feet, or four 2-cubic-foot bags. For other beds and materials, use the Mulch Calculator.