Protecting plants from frost
How to protect your plants from frost
What to cover, how to cover it, and when covers stop working, from Iowa State University Extension. Enter your ZIP for your own frost dates.
Free. No account. Built from NOAA climate records, the USDA hardiness map and university extension guides.
How do I protect my plants from frost?
Bring potted plants into a warm room, porch or garage for the night, and cover tender plants with sheets, blankets or frost fabric held up on stakes so the cover does not touch the leaves. Take the cover off the next day once it is above freezing. Below about 28 °F, covers usually stop working.
Step by step
- Watch the forecast for overnight lows from mid to late September.
- Move potted tropical plants and annual containers into a heated room, a porch or a garage for the night.
- Cover tender plants with sheets, blankets, towels, tarps, frost fabric or row cover, which trap the heat rising from the ground.
- Hold the cover up on stakes, posts, wire loops or patio furniture so it does not touch the leaves.
- Take the cover off the next day, once the temperature is above freezing.
- Expect covers to stop working below about 28 °F, especially when it stays below freezing for more than five hours.
What needs covering
- Cover vegetables, annual flowers and tropical plants.
- Perennials, shrubs, roses and small trees do not need covering, and covering them does not help.
- Spinach, beets, kale, carrots and lettuce usually survive a light frost, often down to 28 °F and sometimes 26 °F.
Frost and freeze
Frost is ice forming on the surface of leaves, which can happen when the air is slightly above freezing; the National Weather Service issues frost advisories for forecast lows of 33 to 36 °F. A freeze is when the air and the inside of the plant fall below 32 °F, which damages the plant's cells and turns the leaves brown or black.
Source: Aaron Steil, "How to Protect Plants from Frost and Freeze", Iowa State University Extension, 2024. Enter your ZIP above for when frost and the 28 °F hard freeze typically come where you live.
Next questions: When is my first frost? · How to get the garden ready for winter
Your exact dates
Frost dates from the NOAA weather station nearest your ZIP, and the sowing and planting dates that follow from them for 34 vegetables and herbs.
What to do this week
The jobs that are open now for the crops you grow, the next one coming, and how many days are left before frost.
Local to you
The garden centres near your ZIP, and the plants native to your state that deer usually leave alone.
How it works
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Your zone, frost dates and this week's jobs appear at once.
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Pick your crops
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- The garden report twice a week: your crops' jobs, and a midweek hint on spotting and treating pests and problems
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Questions
Is it really free?
Yes. The page, your dates, the planting calendar and the monthly report are free, with no account. My Garden adds the twice-weekly report, frost alerts and your garden record for $3 a month or $30 a year.
Where do the dates come from?
Frost dates come from NOAA's 1991-2020 climate normals at the weather station nearest your ZIP. Zones come from the 2023 USDA hardiness map. Planting times come from University of New Hampshire and Purdue extension guides. Every source is named at the bottom of the page.
Does it work where I live?
It covers every ZIP code in the continental US. In the few places that rarely freeze, such as southern Florida and coastal southern California, frost-based planting dates do not apply, and the page says so.
Will you fill my inbox?
The free report comes once a month. My Garden members choose twice a week. Every email has a one-click unsubscribe, and your address is used for nothing else. Privacy.
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See your garden's dates in ten seconds
How to do it
ZIP
How these dates are worked out
What are you growing?
Pick your crops and the page shows only their jobs. Your picks are remembered on this device.
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Your garden this week
Your free monthly garden report
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My Garden sends the report for your crops every week, a midweek hint on spotting and treating pests and problems, and a frost alert when a freeze is forecast at your ZIP. It is $3 a month, or $30 a year.
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Your garden report twice a week, for $3 a month
- The jobs for your crops, every week, timed to ZIP
- A midweek hint on spotting and treating the pests and problems your crops meet at that point in the season
- A frost alert when a freeze is forecast at your ZIP
- Your own schedule and a record of your garden, season after season
Opens in early 2027. Nothing is charged today, and no card is needed.
Garden centres near you
Native plants for your garden
Planting calendar
Dates count from the cautious frost dates the extension guides assume: in spring, the date after which only one year in ten still has frost, and in fall, the date by which one year in ten has had it. Outside the Midwest, New England and New York they sit two weeks inside your typical dates. Crops marked ↻ do best sown or planted in several small batches through their window.
Plants deer usually leave alone
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Where the answers come from
- ZIP code locations: US Census Bureau, 2026 ZCTA Gazetteer and the 2020 ZCTA-to-county relationship file. Some PO-box ZIP codes are located with GeoNames (CC BY 4.0).
- Hardiness zones: the 2023 USDA Plant Hardiness Zone Map by ZIP code, from the PRISM Climate Group, Oregon State University.
- Frost dates: NOAA National Centers for Environmental Information, U.S. Climate Normals 1991-2020, the date of the last spring and first fall 32 °F reading in half of years, at the nearest station that reports them. In the Midwest, New England and New York the page also gives the station's 1-in-10 dates, its 28 °F hard-freeze date, and its rain and snow.
- Soil: USDA NRCS Soil Survey (SSURGO) through Soil Data Access, the mapped soil at the ZIP code's centre point, for the Midwest, New England and New York.
- Planting times: UNH Cooperative Extension, Growing Vegetables: When to Plant, and Purdue Extension HO-186-W, Indiana Vegetable Planting Calendar.
- Deer resistance: Rutgers NJAES, Landscape Plants Rated by Deer Resistance.
- Garden centres: © OpenStreetMap contributors, every US place tagged as a garden centre, with national big-box stores and hydroponics shops left out. The list is available under the Open Database License.
- Native plants: iNaturalist establishment data (plants it marks native in your state, with research-grade sightings there) and its flowering records by month. In the Midwest, New England and New York the list keeps natives that nurseries routinely sell (USDA PLANTS, which also gives heights) or that Rutgers rates for deer, and leaves out weeds and plants that harm people who touch them. Elsewhere it is limited to plants on the Rutgers deer-resistance list.
- Seed shops: the links in the report open each shop's own search page. Garden by Address earns nothing from them at present.
Weather varies from year to year and garden to garden, so treat every date as a guide and watch your local forecast.