Winter Mulch Desk: when to mulch, how deep, and how much to buy
Most winter mulch goes on after a few hard frosts or once the top of the soil starts to freeze, not on a calendar date. Garlic and new trees can be mulched now. Pick your zone and what you see outside, pick what you grow, and the desk tells you mulch now or wait, with the material, depth, and spring removal for each. Then measure your beds to get cubic feet, cubic yards, and bag counts, and download the plan as a CSV. Your answers save on your device. No account needed.
Free winter mulch planner. See when to mulch strawberries, garlic, roses, perennials, bulbs, root crops, and new trees, what material and depth to use, when to pull it off in spring, and how many cubic feet or bags you need. Sourced from university extension.
When to put winter mulch on
Apply protective mulch as soon as the soil begins to freeze, or any time after that (University of Minnesota Extension). Mulch put on too early can keep plants growing under it and weaken them. Snow on top adds insulation. In zones 8 and warmer the ground may not freeze at all, so keep regular mulch on beds and mulch the roots of pots and new plants before a hard freeze (Clemson).
Material, depth, and timing by plant
| Plant | When | Material and depth | Spring |
|---|---|---|---|
| Perennial flowers | After the soil begins to freeze (Minnesota, Iowa State) | About 4 in over crowns (Iowa State); 5 to 6 in of leaves, straw, compost, or corn stalks (Minnesota) | Early spring as the top layer thaws |
| New or borderline hardy perennials | Late fall once dormant, before the ground freezes (Iowa State) | 6 to 8 in of straw, pine needles, or corn stalks in a wire cage; loose straw can go 6 to 18 in (Iowa State) | Early spring before plants break dormancy |
| Grafted roses | After several hard frosts, once dormant (Purdue, New Hampshire) | Mound 10 to 12 in of soil over the base, about 5 gallons per rose (Purdue), then straw or leaves on top (Iowa State) | After the ground thaws, before new growth |
| Strawberries | After 2 or 3 frosts, or once soil at 4 in stays at or below 40 F for 3 days (Minnesota) | 4 to 6 in of clean wheat or rye straw (Minnesota, West Virginia) | When soil reaches about 40 F and new leaves start |
| Garlic | After planting (Minnesota), or once the ground freezes (New Hampshire) | 3 to 4 in of straw or leaves (Minnesota); 4 in (New Hampshire) | Pull back after hard freezes end, or leave for weeds |
| Spring bulbs | After the soil begins to freeze (Minnesota) | 5 or 6 in of leaves, compost, corn stalks, or straw (Minnesota) | Early spring as it thaws |
| Root crops left in the ground | After the first heavy frosts, on cold soil (New Hampshire, UC ANR) | 6 to 8 in of straw or leaves to dig into winter (Illinois, New Hampshire); a foot or more for all winter (UC ANR) | Dig the rest before new tops grow |
| Newly planted trees and shrubs | In fall, before the ground freezes (Minnesota) | 3 to 4 in of shredded wood, pulled 6 in back from the trunk (Minnesota); never over 4 in (Virginia) | Leave it on all year |
How much mulch to buy
Square feet times depth in inches, divided by 12, gives cubic feet. Divide cubic feet by 27 for cubic yards. A 4 by 8 ft bed at 4 in needs about 10.7 cu ft, which is 6 bags of 2 cu ft or 4 bags of 3 cu ft. A 39 gallon lawn bag holds about 5.2 cu ft of loose leaves.
Spring removal
Take crown mulch off perennials and bulbs in early spring as it thaws, and keep a cover handy for a late freeze (Minnesota). Iowa State gives about mid March for perennials and mid March to early April for rose mounds in Iowa. Strawberry straw comes off when soil reaches about 40 F and new leaves start.
Guides
Related
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Sources
- University of Minnesota Extension, Mulch perennials and bulbs after the soil freezes
- University of Minnesota Extension, Protecting trees and shrubs in winter
- University of Minnesota Extension, Growing garlic in home gardens
- University of Minnesota Extension, Growing strawberries in the home garden
- West Virginia University Extension, Getting Strawberry Plants Ready for Winter
- Iowa State University Extension, How should I prepare my perennial beds for winter?
- Iowa State University Extension, How to Overwinter Plants
- Iowa State University Extension, How to Overwinter Roses
- University of New Hampshire Extension, Winter Protection of Roses
- University of New Hampshire Extension, Growing Garlic in New Hampshire
- University of New Hampshire Extension, Fall Vegetable Garden Activities
- Purdue University Consumer Horticulture, Hibernation for Roses
- Nebraska Extension in Lancaster County, Rose Winter Protection
- University of Missouri IPM, Winter Plant Protection
- University of Illinois Extension, Late Season Vegetable Storage Tips
- University of California ANR, Storing Vegetables and Fruits at Home
- Virginia Cooperative Extension SPES-661, Mulching
- Clemson Extension HGIC 2350, Cold Damage