How to Keep Potted Perennials Over Winter in Cold Zones

Updated September 2026 · Garden Advice Guide

To keep potted perennials over winter in a cold zone, start with one rule: a perennial in a pot above ground is about two zones less hardy than the same plant in the ground. A plant rated two zones colder than yours can stay outside in its pot if you group and insulate it. Anything less hardy needs a cold, sheltered spot like an unheated garage or shed, a hole in the ground to sink the pot into, or a trip indoors. Tender perennials such as geraniums come inside before frost, either as houseplants or as dormant roots.

The reason is simple. Roots are far less cold hardy than stems and buds, and in a pot they sit in freezing air instead of insulating soil. Pick the right method for each plant and the pots come through winter ready to grow.

Plan your timing first. Find your average first fall frost with our free frost date lookup. Tender plants move before that date, and hardy perennials move a few weeks after it, once they are dormant.

Updated September 2026

Why Potted Perennials Die Over Winter

Most potted perennials that fail in winter are killed at the root, not the crown. Three things do it.

Roots freeze solid. A perennial's crown, stems and buds harden off gradually through fall and can take very low temperatures. Its roots do not harden nearly as much, because in the ground they never have to. Soil a few inches down in a zone 5 garden under snow usually stays in the 20s or warmer even when the air drops far below zero. Nursery research on container plants has found the roots of many hardy landscape plants damaged somewhere in the range of about 10 to 25°F, while the same plants' tops tolerate -20°F. A pot sitting on a patio can drop to near the air temperature within a day or two, so the roots see cold they would never feel in the ground.

Freeze and thaw cycles. A pot in the sun thaws on a bright afternoon and refreezes that night. Each cycle breaks roots and heaves the root ball, and a pot that goes through dozens of cycles suffers more than one that stays frozen steadily.

Winter drought and winter wet. A frozen root ball cannot take up water, but evergreen leaves and the plant's tissue still lose it, especially in wind and sun. On the other side, a pot that is saturated going into a freeze rots crowns when it thaws and can crack the pot. Both problems are about moisture, and both are easier to manage than cold.

Winter killing of roots is also why the zone on a plant tag does not transfer to a pot. The tag rating describes a plant with its roots in the ground.

The Two Zones Colder Rule

For a perennial to stay outdoors in its pot with only grouping and insulation, choose plants rated at least two zones colder than yours. Plants rated only one zone colder, or rated for your zone, need a storage method from the sections below.

Check your exact zone, including the half zone, with our growing zones lookup. Hardy succulents in pots are the exception that proves the rule, because keeping them dry matters more than keeping them warm, and our guide to cold hardy succulents covers rain shelter for those pots. Pot size shifts the rule a little. A half barrel or a large planter of 20 gallons or more holds cold more slowly than a 2 gallon pot and behaves closer to one zone less hardy, while small pots under a gallon can behave three zones less hardy.

For perennials that are hardy in your area in the ground, our list of perennials by zone gives the ratings, so you can work out which of your pots clear the two zone bar.

How to Keep Potted Perennials Over Winter: Pick a Method per Pot

Match each plant to one of five options.

Mums in pots fit in here too, but whether a potted mum is worth overwintering at all depends on which of the two kinds it is. Our comparison of hardy mums vs florist mums covers that decision and the odds, so it is not repeated on this page.

Unheated Garage and Shed Storage

This is the most reliable method for hardy perennials in pots, because it gives roots steady cold without the deep lows and repeated thaws of an open patio. A dormant perennial needs cold, not warmth, so an attached garage that stays between about 20 and 40°F all winter is close to perfect.

When to move pots in. Wait until the plant has gone dormant, which usually means after two or three hard freezes have killed back the foliage. For most gardens that falls two to four weeks after the first frost date. Moving a plant in while it is still green and growing keeps it awake, and it will try to grow in the dark.

How to do it.

1. Cut back deciduous perennials like hostas, daylilies and coneflowers to a few inches once the foliage has died. Leave evergreen perennials such as heuchera, hellebore and lavender uncut.
2. Water the pot a day or two before moving it, so the root ball goes in evenly moist, not soggy.
3. Group pots together away from the garage door, against an inside wall that backs onto the house if you have one. That wall gives off a little heat.
4. Set a minimum and maximum thermometer among the pots. If it reads above 45°F for long stretches, plants may start growing early. If it drops below about 15°F, wrap the group with an old blanket or move the pots into a large cardboard box stuffed with leaves.
5. Water about once a month. Check the mix with a finger every three or four weeks and give a small drink if it is dry. The aim is a root ball that never goes bone dry and never gets soggy. A frozen pot does not need water until it thaws.
6. Evergreens want some light. Deciduous perennials can sit in the dark. Heuchera, hellebore, evergreen ferns and lavender store better near a window.
7. Watch for mice and voles. A garage full of dormant hosta crowns is a winter pantry. Set traps nearby or stand pots on a table rather than the floor.

When to bring them out. In early spring, once the worst cold has passed and new growth is showing, start setting the pots outside on mild days and bringing them in on nights forecast below the mid 20s. Leave them out for good around your last frost date, putting them in shade for the first week so the pale new shoots do not scorch.

A detached, uninsulated shed runs colder than an attached garage and may track outdoor temperatures within a few degrees on the coldest nights. It still helps by blocking wind and sun, but treat a shed like a sheltered patio and add insulation around the pots.

Grouping and Insulating Pots Outdoors

For plants that pass the two zones colder rule, or when there is no garage space, a well built cluster of pots outdoors works well.

1. Pick a sheltered, shaded spot. A north or east wall of the house, out of the wind, is best for winter-long storage because it stays steadily cold. A south wall that heats up on sunny afternoons causes more freeze and thaw cycles, which damage roots. (A south wall is useful for a single frost night, which is a different job covered in our page on how to protect plants from frost.)
2. Push the pots tightly together. Put the most tender pots in the middle and the hardiest on the outside. A mass of soil holds cold far more slowly than a single pot.
3. Set them on soil or mulch, not decking or concrete. Ground contact helps a little. If the pots must sit on a deck, lay a thick layer of straw or leaves under them first.
4. Fill the gaps. Pack shredded leaves, straw or pine needles between the pots and around the outside of the cluster, up to the rims.
5. Wrap the group. Circle the cluster with chicken wire or a burlap fence, fill that with more leaves, or stack straw bales around it.
6. Cover the tops once the soil freezes. A layer of evergreen boughs or a loose covering of leaves over the crowns is enough. Heavy wet mulch sitting directly on crowns over winter can rot them, so keep it light and airy.
7. Snow is welcome. Pile clean snow over the cluster whenever you shovel. It is the best insulation there is.

Burying Pots in the Ground

Sinking the pot into garden soil gives the roots exactly the conditions their zone rating was based on. It is the most protective outdoor method and suits plants rated for your zone that would be marginal in a garage.

1. Choose a well drained spot. An empty vegetable bed or the edge of a border is ideal. Avoid low areas where water pools in winter, since a buried pot in a wet hole rots.
2. Dig a hole slightly larger than the pot, deep enough that the rim sits at or just below soil level.
3. Set the pot in and backfill around it. Plastic nursery pots are best for this. Terracotta and ceramic pots can crack in the ground just as they do above it, so slide the plant into a plastic pot first or knock it out and plant the root ball directly into the hole.
4. Water it in and let the soil settle.
5. Mulch after the ground freezes with 3 to 4 inches of shredded leaves or straw over the whole area. Mulching earlier invites mice to nest and can keep the soil too warm for dormancy.
6. Mark each pot with a tall stake and a label so you can find it under snow.
7. Lift the pots in spring once the soil has thawed, wipe them off, and move them back to their summer spots.

For many pots, dig a single trench and line them up in a row. This is the old nursery practice called heeling in, and it takes less digging than individual holes.

Bringing Geraniums Indoors

The common bedding geranium (Pelargonium) is a perennial in its native South Africa and in zones 10 and 11, and it dies at the first hard frost everywhere else. Bring it in before your first frost date using any of three methods. The hardy cranesbill geraniums (Geranium species) are a different plant entirely and stay outdoors.

Before any of them, check each plant for aphids, whiteflies and spider mites, and hose the leaves off.

As a houseplant

1. Cut the plant back by about half and remove any flowers and buds.
2. Keep it in the pot, or lift it from the ground into a pot just large enough for the roots.
3. Place it in your sunniest window, ideally south facing, in a room around 55 to 65°F. Warm, dim rooms make weak, stretched growth.
4. Water only when the top inch of mix is dry, and do not fertilize until March.
5. Pinch the tips of stretched stems in late winter to keep it bushy, and move it back outdoors after your last spring frost.

As a dormant plant

This is the old method for people without a sunny window, and it works surprisingly well.

1. Before frost, dig or unpot the plant and shake off as much soil as you can.
2. Cut the stems back by about a third and remove all leaves and flowers.
3. Put each plant in a paper bag, or hang it upside down by the roots, in a cool, dark, dry space around 40 to 50°F, such as a basement or an attached garage that stays above freezing.
4. Once a month, take the plants out and soak the roots in water for an hour, then let them drain and hang them back up.
5. In March, cut the stems back to live green tissue, pot them up in fresh mix, water, and set them in a bright window. New shoots appear in a few weeks.

Expect to lose a few plants this way. The survivors grow into full plants by early summer.

As cuttings

Take 4 inch cuttings from healthy stem tips in September, strip the lower leaves, let the cut ends dry for a few hours, and root them in small pots of moist potting mix in a bright window. Roots form in three to six weeks. A windowsill of cuttings takes far less space than whole plants and gives you young, vigorous geraniums in spring.

Potted Hydrangeas

How to overwinter a hydrangea in a pot depends on which kind it is, because the kinds form their flower buds at different times.

For bigleaf hydrangeas in pots, do not prune in fall, because the stems already carry next summer's flower buds. Move the pot into an unheated garage after the leaves drop and after a few hard frosts, water it about once a month so the root ball never dries out completely, and bring it back out after your last frost. A bigleaf hydrangea that leafs out but never blooms after winter usually lost its flower buds to cold, even though the plant survived.

Panicle and smooth hydrangeas bloom on the current year's growth, so cold that kills stem tips costs you nothing. Prune them in late winter or early spring. For the timing on a popular panicle variety, see when to prune Strawberry Vanilla hydrangea.

Potted Ferns

Ferns split cleanly into hardy and tender types, and the two go in opposite directions for winter.

Hardy ferns such as Christmas fern, ostrich fern, lady fern and Japanese painted fern are rated to zones 3 to 5 depending on the species. Under the two zones colder rule, most can stay outdoors grouped and insulated in zone 6 and warmer, but in zones 5 and colder it is safer to bury the pot or store it in the garage. Deciduous hardy ferns can go into the dark. Evergreen types like Christmas fern keep better near a garage window.

Tender ferns such as Boston fern, Kimberly queen fern and asparagus fern are tropical plants that come indoors before nights fall into the 40s. Kept as houseplants, they want a bright spot out of direct sun, a room around 60 to 70°F, and more humidity than most winter houses offer, so expect some leaf drop. If you have no bright space, a cool basement around 50 to 55°F with the plant cut back and watered lightly once or twice a month keeps it semi-dormant until spring, though it will come out thin and need a few weeks outdoors to fill back in.

Which Pot Materials Crack

When wet mix freezes, it expands and pushes outward on the pot walls. Materials that absorb water are the most likely to split or flake, and pots that narrow at the top trap the ice and crack whatever they are made of.

For plants that stay outside, a simple fix is to grow in a plastic nursery pot slipped inside the decorative one, then lift the plastic pot out in fall and store the decorative pot dry and upside down. The full rundown on frost proof pots for outdoor winter displays is on our page of front door winter planter ideas. Summer potting mix, pot size and drainage are covered in our container gardening guide.

A Zone by Zone Plan

These are typical dates. The dates for your own ZIP code can differ by two weeks or more, so use the frost date lookup for the real numbers and set the plan from those.

Seasonal container displays follow a different calendar. The pots of pansies, kale and other cold tolerant annuals that carry color into winter are covered in our page on fall flowers for pots. This page is about the plants you want to keep for next year.

A Worked Example: Six Pots in Zone 5b

Say you live in zone 5b with an attached, unheated garage, an average first frost around October 10, and six pots on the patio.

1. Three red geraniums in a window box. Tender. On October 1, you take eight cuttings and pot them on a south windowsill, then cut back the best whole plant by half and bring it in as a houseplant. The other two go into paper bags in the basement as dormant plants.
2. A Boston fern in a hanging basket. Tender. It comes in on September 25, when nights reach the mid 40s, and hangs in a bright bathroom.
3. An 'Autumn Joy' sedum in a 14 inch plastic pot. Upright sedum is rated to zone 3, which clears the two zone rule for 5b. You leave it on the north side of the house with the other hardy pots in an insulated cluster.
4. A heuchera in a 12 inch glazed pot. Rated to zone 4, one zone short. The glazed pot is also a cracking risk. On November 5, after several hard freezes, it goes into the garage near the window, still in its pot, since the mix is dry enough not to split it.
5. A bigleaf hydrangea in an 18 inch resin pot. Rated to zone 5 in the ground, and its flower buds are tender. After leaf drop in early November, it goes into the garage against the house wall. You water it on the first of each month.
6. Lavender in terracotta. Rated to zone 5, one zone short, and terracotta cracks. You slide the root ball into a plastic pot, bury it in the vegetable bed on November 1, mark it, mulch it after the ground freezes, and store the terracotta pot upside down in the garage.

In late April you start bringing the garage pots out on mild days. By mid May everything is back on the patio, the geranium cuttings are bushy young plants, and the hydrangea sets flowers because its buds spent the winter above 15°F.

FAQ

Can perennials stay in pots outside over winter?

Yes, if the plant is rated at least two zones colder than your zone and you group the pots together in a sheltered spot with insulation packed around them. A zone 5 gardener can leave a zone 3 perennial outside this way. Plants rated closer to your zone need an unheated garage, a buried pot, or indoor storage, because roots in pots get much colder than roots in the ground.

How do I store potted perennials in a garage over winter?

Wait until the plants are dormant, usually a few weeks after the first frost, then cut back deciduous plants, water the pots, and group them against an inside wall. Aim for 20 to 40°F. Water lightly about once a month so the root balls never dry out completely, give evergreens some light from a window, and bring the pots out in spring as new growth starts.

Should I water potted perennials in winter?

Yes, sparingly. Check stored pots every three or four weeks and water when the mix is dry to the touch, giving just enough to moisten it. A frozen pot does not need water until it thaws. Dry root balls are one of the most common winter losses, but soggy pots rot, so the aim is barely moist.

Can I bury potted plants in the ground for winter?

Yes, and it is one of the most protective methods. Dig a hole in a well drained spot, set the pot in so the rim sits at soil level, backfill, and mulch over the top after the ground freezes. Use plastic nursery pots, since terracotta and ceramic can crack. Mark each pot so you can find it, and lift them in spring once the soil thaws.

How do I keep geraniums over winter?

Bring them in before the first frost. Keep them as houseplants in a sunny window at 55 to 65°F after cutting them back by half, store them dormant in paper bags in a cool dark basement with a monthly root soak, or take 4 inch cuttings and root them on a windowsill. Replant outdoors after the last spring frost.

Do terracotta pots crack in winter?

Often, yes. Unglazed terracotta absorbs water, and when the water in the clay and the wet mix inside freezes, it expands and flakes or splits the pot. Empty terracotta pots and store them dry for winter, or move the plant into a plastic pot. Plastic, resin, fiberglass and wood are safe to leave out in freezing weather.

When should I bring potted perennials inside?

Tender perennials like geraniums, Boston ferns and rosemary come in before your first fall frost, and ideally before nights drop into the 40s. Hardy perennials going into a garage should wait until they are dormant, after two or three hard freezes. Bringing a hardy plant in while it is still green keeps it growing in the dark and weakens it.

Can a potted hydrangea stay outside in winter?

Panicle and smooth hydrangeas, rated to zone 3, can stay outside in grouped and insulated pots in zone 5 and warmer. Bigleaf hydrangeas carry next year's flower buds through winter, and those buds are easily killed by cold, so move bigleaf hydrangeas in pots into an unheated garage in zone 7 and colder. Do not prune them in fall.