🧭 Garden systemContainers8 stepsFree working copy
Overwintering plants in pots: a winter plan for every pot
Quick answer
Roots in a pot get far colder than roots in the ground, so give every pot that holds a perennial its own winter plan. Pots that stay outside need plants hardy two zones colder than your yard, grouped against a sheltered wall and mulched heavily. Pots you can carry go into a garden bed after the first frost, under 6 to 12 inches of straw. The rest go into an unheated garage or shed at about 20 to 45°F and get water every two to three weeks.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026; Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
Decide first
Does this pot need a winter plan?
Do it yourself
Plan it this fall
Make a plan for every pot that holds a perennial, a shrub or a hardy herb you want back next year. You need the plant tags, your zone, and either a spade and some straw or a spot in an unheated garage. Sorting a typical patio takes about an hour; the moving waits for the first frost.
Skip it
Let the annuals go
Annual flowers and summer vegetables finish with the frost, so they don't need a plan. Pull them, compost what you can, and stack the empty pots out of the weather. A plant that isn't hardy anywhere near your zone is easier to treat as an annual too.
Get help
Ask a nursery about the plant
If a tag is lost or you don't know what the plant is, take a photo or a cutting to a local nursery or your county extension office and ask for its hardiness zone. This page covers where each pot spends the winter, not identifying plants.
- 2 zonescolder than your yard: what a pot that stays out should be hardy toIllinois Extension, overwintering potted plants, October 6, 2026
- 6 to 12 inof straw or pine needles over pots buried in a bedIowa State Extension, overwintering unplanted trees, shrubs and perennials, October 7, 2026
- 20 to 45°Fthe range for an unheated garage or shedIowa State Extension, overwintering unplanted trees, shrubs and perennials, October 7, 2026
- 2 to 3 weeksbetween waterings in storage when it's above freezingIowa State Extension, overwintering unplanted trees, shrubs and perennials, October 7, 2026
From the first frost to spring
The steps, in order
Check every tag against your zone
List every pot you want to keep and read the lowest zone on each tag. Illinois Extension says a plant that winters outside in a pot should survive two zones colder than where it grows. In zone 6, the tag should reach zone 4.
Have ready: Your zone, the plant tags and the working copy.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026.
Give each pot a plan
Write one plan beside each pot. Bury the ones you can carry to a bed. Group the heavy ones whose tags pass the two-zone check. Store the rest, and anything that lives on a deck or balcony, in an unheated garage or shed.
Have ready: The pot list and a pencil.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026; Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
Water everything well
Before the pots go anywhere, water each one thoroughly. Illinois Extension says to make sure the plants are well watered going into winter and to check them through the season.
Have ready: A hose or a watering can, on a day above freezing.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026.
Bury pots after the first frost
Within a few weeks after the first fall frost, dig a hole in a garden bed for each pot you're burying, set the pot in, and pack soil around it as if you were planting it.
Have ready: A spade and open soil in a bed.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
Cover buried pots with straw
Once the plants are dormant, spread 6 to 12 inches of straw, pine needles or other loose mulch over the buried pots. Iowa State Extension advises against leaves for this job, because they pack down.
Have ready: A bale of straw or a few bags of pine needles.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
Group the heavy pots
Cluster the pots that stay out on the north or east side of a building, out of strong wind and too much sun, and set them on the ground rather than on a deck. Heap straw, leaves or wood mulch around them.
Have ready: A sheltered wall, a hand truck for big pots, and mulch.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026; Illinois Extension, overwintering perennial patio containers, checked October 7, 2026.
Store the rest cold, and water them
Move the remaining pots into an unheated garage, shed or cool basement once the plants are dormant. Iowa State Extension's range is about 20 to 45°F, with water as often as every two to three weeks while it's above freezing.
Have ready: Floor space out of the car's way and a reminder on your phone.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
Bring them back in spring
Iowa State Extension takes the straw off around mid-March in Iowa; go by your own weather. Lift the pots, put them back out, and top up any mix that sank. Note on the working copy which plan worked for which pot.
Have ready: A ruler, a bag of potting mix and the working copy.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
Free, one page, black and white
Print the working copy
Pot winter plan: the steps above as a checklist with a date box for each, on one US Letter page.
If a step gets skipped
What goes wrong
⚠️
Leaving a small pot up on the deck
Above ground, the mix in a pot can drop into the single digits, Iowa State Extension says, cold enough to damage the roots. Illinois Extension adds that grouped pots are better protected on the ground than on a deck.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026; Illinois Extension, overwintering perennial patio containers, checked October 7, 2026.
⚠️
Burying under leaves
Leaves look like a free cover, but Iowa State Extension advises against them over buried pots because they pack down. Use straw or pine needles there and keep the leaves for the grouped pots.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
⚠️
Storing pots somewhere warm
A heated room or a warm basement sits well above Iowa State Extension's 20 to 45°F range. Pick the coldest unheated space you have instead.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
⚠️
Forgetting the garage pots
Out of sight, the stored pots dry out. Iowa State Extension says they may need water as often as every two to three weeks when it's above freezing, so set a reminder before you close the door.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
When the steps change
Variants
🪴
Big pots you can't lift
Leave them where they are, or roll them to a sheltered wall on a hand truck, and mulch around them. Illinois Extension says large containers give roots more cold protection than small ones, so the biggest pots are the best ones to leave out.
Source: Illinois Extension, overwintering perennial patio containers, checked October 7, 2026.
🏙️
A balcony or deck with no ground
There is no bed to bury in, and pots up on a deck lose the warmth of the ground. If you have an unheated garage or shed, the cold-storage plan is usually the one that fits.
Source: Illinois Extension, overwintering perennial patio containers, checked October 7, 2026.
❄️
Cold zones, 3 to 5
The two-zone check gets strict here: a zone 4 yard needs a tag that reaches zone 2. Fewer plants pass, so more pots go into the ground or the garage.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026.
☀️
Mild zones, 8 and up
The same check is easier to pass. In zone 8 a tag only has to reach zone 6, so more of your pots can stay outside, grouped and mulched, with a watering check now and then.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026.
What people learn the second year
Tips and tricks
- Stake the buried pots. Push a plant label or a short stick in beside each buried pot. By January, under a foot of straw, the bed looks empty, and the stakes keep you from putting a spade through a root ball in spring.
- Put a thermometer in the garage. A cheap min-max thermometer tells you whether the garage really stays in Iowa State Extension's 20 to 45°F range, or drops below it on the coldest nights. (Iowa State Extension, overwintering unplanted trees, shrubs and perennials)
- Water by feel, every second weekend. Set one reminder for every other weekend. Push a finger 2 or 3 inches into the mix, the test WSU Extension gives for containers, and water only if it's dry and not frozen. (WSU Extension, Container Gardening tip sheet 6)
- Buy next year's perennials with the tag in mind. When you shop in spring for a pot that will live outside, take your zone minus two with you and read the low end of the tag before you buy.
- Keep the plan with the pots. Tape the working copy inside the garage door. Next fall, the sorting is already done.
The one we checked the steps against
Primary source
Overwintering Unplanted Trees, Shrubs and Perennials, Iowa State University Extension and Outreach, Yard and Garden. Checked October 7, 2026.
Iowa State University Extension's Yard and Garden page on overwintering unplanted trees, shrubs and perennials (February 2025) supplies most of the steps here. Roots are far less hardy than the parts above ground, and mix in a pot above ground can drop into the single digits. It says to bury pots within a few weeks after the first frost under 6 to 12 inches of loose mulch, or store them at about 20 to 45°F and water every two to three weeks when it's above freezing. The two-zone rule and grouping come from Illinois Extension.
The arithmetic and the background reading
Tools and guides in this system
- 🏺 CalculatorContainer soil calculatorHow much potting mix to buy for round pots, square planters and window boxes: quarts, cubic feet and bag counts, filled an inch below the rim.Open the tool
- 🌡️ LookupUSDA zone finder by zip codeFind your 2023 USDA plant hardiness zone by zip code, see its winter low band in °F and °C, and check a plant tag's zone range against it.Open the tool
🧰 Problem solverBury it, group it or garage it: a winter plan for every potPotted perennials die in winter when their roots freeze. Three extension-backed winter plans, how to pick one per pot, and a checklist.Read the guide 
📘 Know-howThe two-zones-colder rule for plants that winter in potsWhy a perennial that winters outside in a pot needs a tag rated two zones colder than your yard, with a zone-by-zone table and a tag check.Read the guide
Common questions
Questions
Can potted perennials stay outside all winter?
Some can. Illinois Extension says to pick plants that survive two zones colder than where they grow, so in zone 6 the tag should reach zone 4. Group those pots against a sheltered wall, on the ground, and mulch heavily around them. Pots whose tags don't pass go into a bed or an unheated garage.
Source: Illinois Extension, overwintering potted plants, checked October 6, 2026; Illinois Extension, overwintering perennial patio containers, checked October 7, 2026.
When should I bury potted plants for winter?
Iowa State Extension says within a few weeks after the first fall frost. Cover them with 6 to 12 inches of straw or pine needles once the plants have gone dormant.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
Do potted plants in an unheated garage need water?
Yes. Iowa State Extension says they may need water as often as every two to three weeks while temperatures are above freezing. Check the mix with a finger first, and skip it if the mix is frozen.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
How cold is too cold for storing pots in a garage?
Iowa State Extension's range for an unheated building is about 20 to 45°F. A min-max thermometer on the wall tells you whether your garage stays in it.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026.
Can I cover buried pots with leaves?
Iowa State Extension advises against leaves over buried pots because they pack down, and names straw, pine needles or other loose mulch instead. Leaves are fine heaped around grouped pots above ground, which Illinois Extension lists among its mulches.
Source: Iowa State Extension, overwintering unplanted trees, shrubs and perennials, checked October 7, 2026; Illinois Extension, overwintering potted plants, checked October 6, 2026.
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Sources
- Overwintering potted plants, University of Illinois Extension, published November 27, 2024. Checked October 6, 2026.
- Overwintering Unplanted Trees, Shrubs and Perennials, Iowa State University Extension and Outreach, Yard and Garden. Checked October 7, 2026.
- Overwintering Perennial Patio Containers, University of Illinois Extension, Hort in the Home Landscape blog, published November 10, 2014. Checked October 7, 2026.
- Puget Sound Gardening Tip Sheet #6: Container Gardening, Washington State University Extension, King County Master Gardener Program. Checked October 7, 2026.
Planning guide, not a guarantee. See every source on the site on the sources page. Spotted an error? Tell us.