How to Overwinter Potted Plants: Winterize Pots Step by Step

How to winterize potted plants: sort them first

To overwinter potted plants, sort them into groups before frost and give each group its own treatment. Tropical plants come indoors when nights dip consistently into the 50s F. Hardy trees, shrubs and perennials stay cold and dormant, either sunk in the ground, grouped and mulched, or kept in an unheated garage at 20 to 45 degrees F. Tender plants that can go dormant are stored cool and dark at 40 to 50 degrees F, and tender bulbs at 40 to 55 degrees F. Empty pots are stored upside down.

Sort every pot into one of these groups before frost, because each group goes to a different place for winter.

The sorting matters because the groups need opposite things. A hardy shrub needs cold to stay dormant, so a warm living room is the wrong place for it. A tropical hibiscus is harmed long before the temperature reaches 32 degrees F. A fuller plant-by-plant list is in our guide to overwintering container plants.

Tropical and houseplant types: move indoors to bright light.
Hardy trees, shrubs and perennials: keep cold, and insulate the roots.
Tender plants that tolerate dormancy, such as geraniums, bananas and angel’s trumpet: store cool and dark.
Tender bulbs such as canna, dahlia and gladiolus: cut back and dig at the first killing frost, then store.
Spent annuals: compost the plants and empty the pots.

Why plants in pots need winter protection

A plant that is hardy in your garden is not automatically hardy in a pot. Iowa State University Extension states it directly: the roots of most trees and shrubs are far less cold hardy than their aboveground stems or trunks. In the ground, that weakness is hidden because soil holds heat.

Weather station data published by Iowa State in 2025 shows how much. On days when air temperatures dropped to minus 15 degrees F or lower, soil 4 inches down averaged 37 degrees F warmer than the air, and soil 12 inches down was about 46 degrees F warmer. The 4-inch soil temperature never fell below 7 degrees F, and the 12-inch reading stayed above 24 degrees F. An exposed container has no such buffer, and Iowa State notes that its potting mix will likely get very close to air temperature.

University of Illinois Extension turns this into a buying rule. Choose plants rated two hardiness zones colder than your own if they will spend winter in a pot. In zones 5 and 6, that means plants hardy to zone 3 or 4. Anything less hardy than that needs one of the methods below.

Hardy plants that stay outdoors

There are three reliable ways to protect hardy plants in containers, and all of them start the same way. Water the pots well before they go into storage. Illinois Extension notes that moist growing media freezes more slowly than dry media, which adds protection.

Sink the pots in the ground. Iowa State’s instruction is to dig holes in a garden area and set the pots in the ground. The surrounding soil insulates the pot and the roots from extreme cold and from temperature swings. Do it after the plants go dormant but before the soil freezes.

Group and mulch. Where digging is not possible, Illinois Extension suggests grouping pots together in a protected location on the north or east side of a building and mulching them heavily with straw, leaves or wood mulch. Iowa State gives depths: 6 to 18 inches of loose material such as straw or pine needles, or 3 to 4 inches of a heavier mulch such as shredded bark or wood chips. In Iowa the mulch goes on in early to mid-November and comes off around mid-March. Shift those dates to match when the ground freezes and thaws where you live.

Move them to an unheated building. An attached, unheated garage, a shed or a cold basement works if it holds 20 to 45 degrees F. That range keeps plants dormant without exposing roots to deep cold. Iowa State adds a condition: the space is suitable only if temperatures stay consistently in that range, so monitor it. A thermometer near the pots does the job.

Tender plants that come indoors

Houseplants that spent summer outside, and tropicals such as hibiscus, need to move before cold nights arrive. Iowa State’s guidance is to bring them in when nighttime temperatures dip consistently into the 50s F. Many indoor plants show damage in the mid to lower 40s F, and nearly all will die if exposed to temperatures below freezing.

Clean them up outside first. Check for insects, rinse all the foliage thoroughly and let it dry before the plant crosses the threshold. Then keep new arrivals isolated from other houseplants for 3 to 4 weeks, since scale, mealybugs and aphids usually show themselves within about a month. If mites appear, see how to get rid of spider mites on houseplants.

Indoors, place the plants in bright, indirect light and expect some leaf drop, especially from tropical hibiscus and weeping fig. Even the brightest spot in a house gets a fraction of the light found in outdoor shade. Stop fertilizing through fall and winter, when the plants are not actively growing, and water only when the soil is dry. Rosemary and bay follow slightly different rules, covered in overwintering rosemary, bay and tender herbs.

Storage temperatures for overwintering plants

Three temperature ranges cover nearly every stored pot, and they are worth checking against the spaces you have. A garage that suits dormant shrubs can be too cold for geraniums.

The hardy band reaches well below freezing while the two tender bands sit entirely above it, so the groups cannot share the coldest spaces.

What you are storing	Temperature	Light	Water
Hardy trees, shrubs and perennials in pots	20 to 45 degrees F	Not needed while dormant	Once every two to three weeks if above freezing
Dormant tender plants: geranium, banana, angel’s trumpet	40 to 50 degrees F	Dark	Light watering every 2 to 4 weeks
Tender bulbs: canna, dahlia, gladiolus	40 to 55 degrees F	Dark	Stored out of the pot
Tropical plants kept growing	Normal room temperature	Bright, indirect	When the soil is dry

For the dormant tender group, Iowa State advises a cool, dark place at 40 to 50 degrees F. Tender bulbs are cut back immediately before or after a killing frost in fall, pulled, and held in a cool, dark, dry place at 40 to 55 degrees F. Our guide to overwintering dahlias and tender bulbs covers digging and packing.

How to care for overwintering plants until spring

Stored plants still need attention, and most of it is water. A pot in a garage gets no rain or snow for months.

Hardy pots under cover: check soil moisture often. Iowa State says water may be needed as often as once every two to three weeks if temperatures are above freezing.
Hardy pots outdoors: check through the winter, especially evergreens, which Illinois notes are prone to winter burn when they dry out.
Dormant tender plants: a light watering every 2 to 4 weeks prevents excessive drying.
Tropicals indoors: water when the soil is dry, hold the fertilizer, and keep checking for pests.

Look at the thermometer when you water. Iowa State’s advice for garages and sheds is to monitor the temperature and adjust it if the space drifts outside 20 to 45 degrees F.

What to do with the pots themselves

Containers suffer in winter as well. Illinois Extension warns that most containers can be damaged by freezing and thawing if growing media is left in them, and recommends removing the media and storing empty pots upside down. Terra cotta and clay have a problem of their own. Water held in the pores of the clay expands when it freezes and cracks the pot, so these need to be dried, protected or brought indoors. If you are choosing containers that will stay planted outside all year, terracotta vs. plastic vs. fabric pots compares the materials.

Bringing overwintered plants back out

Reverse the process slowly. Tropical plants go back outside after the last frost, and Iowa State recommends acclimating them to outdoor light gradually over 2 to 3 weeks. Begin fertilizing every 2 to 4 weeks in late winter or early spring as growth picks up.

Dormant tender plants need a longer runway. Move them into brighter light gradually over 2 to 4 weeks and plant them outdoors after frost. Tender bulbs can be planted outside after the last frost or potted up indoors in late winter for a head start. Hardy pots are the easy group: pull the mulch back around mid-March in a climate like Iowa’s, or lift the pots from the ground, and let them wake up with the season. The same gradual exposure used for hardening off seedlings applies to any plant leaving a dim room.

Quick recap

Sort pots before frost: tropicals indoors, hardy plants cold and insulated, dormant tender plants and bulbs in cool, dark storage.
Roots are less hardy than stems. Pick plants two zones colder than yours for year-round pots, or protect them.
Keep hardy pots at 20 to 45 degrees F, dormant tender plants at 40 to 50 degrees F and tender bulbs at 40 to 55 degrees F.
Mulch grouped pots with 6 to 18 inches of loose material or 3 to 4 inches of heavier mulch.
Check moisture all winter, and empty terra cotta and clay pots so they do not crack.