How to
Mulch the vegetable garden
The summer crops are in and growing, and the soil has finally warmed. Cover it now, before the dry spells and the weeds.
Grown in Ohio, zone 6a. Your frost dates move the calendar; the signals don't. Broadfork goes by where your garden is, not its zone: frost dates for your ZIP code in the US, or the ones you type in anywhere else.
Six minutes to read. The steps stand on their own.
Before you start#
A layer over the soil holds the water in and keeps the weeds down. It also stops rain splashing soil up onto the leaves, and the leaf diseases ride on that splash.
It keeps the soil cool. Straw, shredded leaves or paper can hold it as much as 20 to 25 degrees cooler; some data says nearer 10. Broccoli and greens like that. Tomatoes and peppers don't, which is why the timing matters.
Pick a mulch that rots within the season for beds you plant every year: straw, hay, leaves, clippings or compost. The ones that last for years belong under permanent plantings.
When to lay it#
Mulch keeps cold soil cold. Laid on warm-season crops before the soil has warmed, it slows the roots and the plants and costs yield. Wait for warm soil: about early June for tomatoes.
Peppers are fussier. Early mulch can damage their new roots, and some data waits until July.
Go by the soil, not the date. Check its warmth 2 to 4 inches down. Sandy soil warms sooner than heavy clay.
Black plastic works the other way: it warms the soil, so it goes down before you plant. Straw and the other organic mulches wait.
Short season Where the season is short and the spring cool, the soil may not warm until mid to late June. Wait for it anyway.
Mild winter Where it's warm, the data mulches soon after transplanting. Mulch also rots faster in warm, humid weather.
In Broadfork In Broadfork, a mulch recorded on a tomato bed before June brings a note: it keeps the soil cool, and that costs yield.
What to use#
- Straw
- One of the best for vegetables, because most of it has rotted by the season's end. Buy it seed-free. Its carbon runs 80 to 1 against nitrogen, so it can take nitrogen from the soil while it rots.
- Hay
- It often carries weed seed, so use clean hay or none. Alfalfa or clover hay gives nitrogen back to the soil as it breaks down.
- Shredded leaves
- Free, and they give back calcium, potassium and magnesium as they rot. Shred them, or they mat into a sheet. The data runs 2 to 4 inches deep; one source stops at 2.
- Grass clippings
- They rot fast, at 15 to 1, and give nitrogen back. Dry them first and lay them thin: a quarter inch at a time, built up to about an inch, or 2 to 3 inches once dried for 2 or 3 days. Only from a lawn with no weed killer on it.
- Compost
- It feeds the plants as it breaks down. Top it up through the summer.
- Wood chips
- Keep them out of beds you plant every year. They take years to rot, they get in the way of the next seedbed, and small chips draw nitrogen from the soil.
- Pine needles
- They last 2 to 4 years, which puts them with permanent plantings in some data; some lays them around tomatoes. They don't change soil pH unless you dig them in.
In Broadfork In Broadfork, record a mulch on a bed and the bed's card says what that material gives the soil, with the source under Why.
The steps#
- Weed and water first. Lay it on moist, weed-free soil, once the crop has begun to grow.
- Spread 2 to 4 inches. Most data says 2 to 3 or 2 to 4 inches of straw or leaves. One source lays only about an inch, because more keeps the soil wet.
- Keep it off the stems. Leave 2 to 3 inches of bare soil around each plant. Mulch piled against a stem shelters voles.
- Top it up as it thins. Leaves and clippings rot very fast and need adding to often. Compost gets topped up through the summer, and clippings can take a new thin layer every week.
If it goes wrong#
- Weeds coming up through it
- Seed came in with it: straw can hold grain heads that sprout, and hay brings weed seed. Pull them, and buy seed-free straw next time.
- A wet, sour mat of clippings
- Too thick, or too fresh. Break it up, and dry the next batch before you lay it, thin.
- Slugs
- They lay eggs in the cool, damp under mulch. Keep it to 3 inches or less, 1 inch where they're bad, and keep fresh clippings off the bed. If they keep coming, take the mulch off.
- Yellow, slow plants
- Straw and leaves are high in carbon, and the microbes rotting them take nitrogen first. Give the crop extra nitrogen early in the season, and don't dig fresh mulch in at planting.
- Twisted, cupped leaves
- Weed killer in the hay, clippings or compost, which can stay active for years. Cover your soil for winter has the pot test to run before you use any.
At the end of the season#
Straw, hay, leaves, clippings and compost have mostly rotted by the end of the growing season. Turn them in then, or the next spring.
Or leave it on over winter, where it holds the soil against wind and rain. Cover your soil for winter has the rest.
Under squash, melons and cucumbers, clear it off when the season ends. Cucumber beetles and squash bugs spend the winter in it.
In Broadfork In Broadfork, a straw, leaf or clipping mulch you never mark as taken off thins on the Map as it rots, until the bed shows its soil again.
The exceptions, by crop#
- Tomatoes: 2 to 3 inches, about early June, once the soil is warm. Where it's warm, soon after planting.
- Peppers: 3 to 4 inches, only after the soil has warmed. Some data waits until July.
- Cucumbers: hold straw or compost until the soil passes 75 °F. Black plastic warms it sooner.
- Potatoes: a straw mulch 4 to 6 inches deep can stand in for hilling.
- Lettuce: straw or clippings with no weed killer hold the water and cool the soil. Keep it thin where slugs are a problem.
- Onions: their thin leaves don't shade out weeds, so mulch them: 1 to 2 inches of straw between the rows, or 3 to 4 of straw or clippings.
- Garlic: the straw goes on in fall, after planting, and stays on the bed through spring as a mulch.
- Strawberries: their straw goes on for winter, once the plants go dormant. Mulch strawberries for winter has the dates.
Every number on this page comes from a published extension source.
Sources for this guide: Ohio State University Extension, University of Minnesota Extension, Iowa State University Extension and Outreach, University of Georgia Extension, University of Illinois Extension, University of Missouri Extension, Clemson Cooperative Extension, NC State Extension, Utah State University Extension, Colorado State University Extension, University of California, University of Florida, University of New Hampshire Extension, University of Wisconsin-Madison Division of Extension, WVU Extension, Cornell Cooperative Extension, NDSU Extension, Penn State Extension, Purdue Extension, Rutgers NJAES Cooperative Extension, SDSU Extension, Texas A&M AgriLife Extension, UMass Extension, University of Maryland Extension, University of Vermont Extension, Virginia Cooperative Extension.
The documents behind this guide (71)
- Composting at Home (2021), Ohio State University Extension
- Cucumber Beetles in Cucurbits: Identification, Damage, and Strategies for Control (2026), Ohio State University Extension
- Growing Garlic in the Garden, Ohio State University Extension
- Growing Onions in the Garden (2018), Ohio State University Extension
- Growing Peppers in the Home Garden (2017), Ohio State University Extension
- Growing Strawberries in the Home Garden (2017), Ohio State University Extension
- Growing Tomatoes in the Home Garden (2017), Ohio State University Extension
- Slugs and Their Management in Landscapes (2022), Ohio State University Extension
- Understanding Soil Microbes and Nutrient Recycling (2010), Ohio State University Extension
- Cucumber beetles (2026), University of Minnesota Extension
- Extending the growing season: start early, end later (2024), University of Minnesota Extension
- Growing cucumbers in home gardens (2026), University of Minnesota Extension
- Growing garlic in home gardens (2026), University of Minnesota Extension
- Growing lettuce, endive and radicchio in home gardens (2024), University of Minnesota Extension
- Growing onions in home gardens (2024), University of Minnesota Extension
- Growing peppers (2026), University of Minnesota Extension
- Mulching for soil and garden health (2026), University of Minnesota Extension
- All About Onions (2024), Iowa State University Extension and Outreach
- Compost Ingredients for Home Gardeners: What to Use and What to Avoid (2026), Iowa State University Extension and Outreach
- Growing Leafy Greens in Iowa (2022), Iowa State University Extension and Outreach
- Growing Tomatoes in the Home Garden (2024), Iowa State University Extension and Outreach
- How can I control squash bugs? (2024), Iowa State University Extension and Outreach
- What mulches work well for weed suppression in the vegetable garden? (2024), Iowa State University Extension and Outreach
- Composting and Mulching (2026), University of Georgia Extension
- Georgia Homegrown Tomatoes (2021), University of Georgia Extension
- Growing Cucumbers in the Home Garden (2024), University of Georgia Extension
- Home Garden Lettuce (2022), University of Georgia Extension
- Home Garden Peppers (2026), University of Georgia Extension
- Mulching Vegetables (2022), University of Georgia Extension
- Cucumber, University of Illinois Extension
- Peppers, University of Illinois Extension
- Potato, University of Illinois Extension
- Put your garden to bed with fall/winter cover crops! (2021), University of Illinois Extension
- Squash Bug, University of Illinois Extension
- Vole, University of Illinois Extension
- Grass Clippings, Compost and Mulch: Questions and Answers (2026), University of Missouri Extension
- Growing Home Garden Tomatoes (2022), University of Missouri Extension
- Growing Sweet Peppers in Missouri (2026), University of Missouri Extension
- Mulches (2017), University of Missouri Extension
- Cucumber (2023), Clemson Cooperative Extension
- Mulch (2016), Clemson Cooperative Extension
- Pepper (2023), Clemson Cooperative Extension
- Growing Tomatoes in the Home Garden (2026), NC State Extension
- Herbicide Carryover in Hay, Manure, Compost, and Grass Clippings (2024), NC State Extension
- Leaf Mulch, Free Soil Amendment (2021), NC State Extension
- How to Grow Cucumber in Your Garden (2020), Utah State University Extension
- How to Grow Lettuce in Your Garden (2020), Utah State University Extension
- Potatoes in the Garden (2020), Utah State University Extension
- 1850 - When to Mulch Vegetables, Colorado State University Extension
- Mulches for the Vegetable Garden (2023), Colorado State University Extension
- Cultural Tips for Growing Lettuce (2026), University of California
- Mulching Your Garden (2025), University of California
- Lettuce, University of Florida
- Plant Detail: Peppers (2020), University of Florida
- Garden Mulches [fact sheet], University of New Hampshire Extension
- Growing Vegetables: Tomatoes [fact sheet], University of New Hampshire Extension
- Homegrown Tomatoes for Wisconsin (2017), University of Wisconsin-Madison Division of Extension
- Mulches for Home Gardens and Plantings (2011), University of Wisconsin-Madison Division of Extension
- Growing Peppers in West Virginia, WVU Extension
- Growing Tomatoes in West Virginia, WVU Extension
- Lettuce (2006), Cornell Cooperative Extension
- Putting the garden to bed (2022), NDSU Extension
- Strawberry Plants and Winter, Ready or Not? (2024), Penn State Extension
- Tomatoes (2026), Purdue Extension
- Mulches for Vegetable Gardens (1997), Rutgers NJAES Cooperative Extension
- Organic Garden Mulches To Conserve Moisture and Prevent Weeds (2021), SDSU Extension
- Easy Gardening: Irish Potatoes (2014), Texas A&M AgriLife Extension
- Soil Basics Part III: Organic Matter, Key to Management (2013), UMass Extension
- Winterizing the Vegetable Garden and Composting (2025), University of Maryland Extension
- Tips for Growing Great Tomatoes (2023), University of Vermont Extension
- Mulching: Purpose, Benefits, and Essential Information (2025), Virginia Cooperative Extension
Updated 11/11/2026 · Checked against our sources 11/12/2026