How to overwinter geraniums: 3 methods that work

Bring geraniums indoors before a hard frost. Pick one of three methods. Keep the plant in its pot in a bright, cool window and water it sparingly. Store it bare-root in a cool, dark spot and check it once a month. Or root cuttings and grow them on a sunny sill. All three work. Zonal and ivy geraniums (Pelargonium spp.) cannot take frost, so move them in when nights drop near 40°F (4°C). If frost has already hit, bring them in now and cut off the blackened growth.

Which overwintering method to pick

Choose by the space you have and the time you want to spend.

A sunny window and a few minutes a week? Keep the plant potted. It is the easiest method and the plant may even bloom a little. A cool basement, closet, or unheated garage that stays above freezing? Store the plant bare-root. It takes the least space and the least care. Short on room for big plants? Take cuttings. Ten cuttings fit in the space of one mature geranium.

Many gardeners use two methods at once. A pot in the window is the backup, and a few cuttings are the second backup.

Why geraniums need to come inside

The geraniums sold as garden annuals are tender perennials. They live through winter outdoors in USDA zones 10 and 11. In colder zones, frost kills the leaves and stems, and a hard freeze kills the roots.

If you are not sure when frost will hit, read my guide on what temperature to cover plants for frost. A light frost can blacken leaves but leave the plant alive. A plant with firm stems and a few green leaves is worth saving.

Look up your zone with my post on how to find your growing zone if you do not know it.

Check the plants for pests first

Do this before any plant crosses the door. Indoor air is dry and warm, and pests multiply fast there.

Look under the leaves and along the stems for whiteflies, aphids, and the fine webbing of spider mites. Spray the whole plant with water from the hose. Treat any bugs you find with insecticidal soap, and repeat in a week. My guides on spider mites and aphids show what each pest looks like.

Pick off yellow and dead leaves. Dead leaves invite gray mold, a fungus that spreads in cool, damp rooms.

Method 1: keep geraniums growing in a pot

This method works for plants already in containers. You can also dig a bedding plant and pot it up in a clean pot with drainage holes.

1. Cut the plant back by about half. This leaves a compact plant that is easier to fit in a window.
2. Pot it in fresh potting mix if you dug it from the ground. Water it once, then let the water drain.
3. Set it in the brightest window you have. A south-facing window is best. A room that stays 50°F to 65°F (10°C to 18°C) suits geraniums well.
4. Water when the top inch of soil feels dry. Geraniums rot in wet soil, so err on the dry side.
5. Skip fertilizer until late winter.

Expect the plant to look thin. Short winter days slow growth, and stems stretch toward the light. A grow light fixes that. See my picks for the best grow lights for seedlings. They work for geraniums too.

Method 2: store geraniums bare-root

This method puts the plant to sleep. It needs a spot that is cool, dark, and above freezing. Many gardeners aim for roughly 45°F to 55°F (7°C to 13°C).

1. Dig the plant before frost. Shake off as much soil as you can.
2. Cut off the leaves. Leave the stems and roots.
3. Put each plant in a paper bag, or hang it upside down by the roots from a rafter or hook.
4. Check it once a month. Remove any mold or soft, rotten spots.
5. If the stems look shriveled, soak the roots in water for a few hours. Then hang the plant again.

Some plants will not make it through. Stems that turn mushy or black are done. Keep a few cuttings going as insurance.

A paper bag lets air move. A plastic bag traps moisture and rots the plant. Use paper.

Method 3: root geranium cuttings

Cuttings take little room and give you fresh, young plants in spring. Take them in fall before the parent plant declines.

1. Cut a 3 to 5 inch tip from a healthy stem. Cut just below a leaf node, where a leaf joins the stem.
2. Strip the lower leaves. Pinch off any flowers or buds so the cutting puts its energy into roots.
3. Let the cut end dry for a few hours. Geranium stems rot if you stick them in soil while they are fresh and wet.
4. Fill a small pot with moist potting mix or a mix of potting soil and perlite. Poke a hole with a pencil and set the cutting in it. Firm the mix around the stem.
5. Put the pot in bright light. Do not cover it with plastic. Moist, closed air rots geranium cuttings.
6. Water when the top of the mix dries out.

Roots form in a few weeks. Tug a cutting. If it resists, it has roots. New leaf growth is another sign. Move rooted cuttings to their own pots.

Gnats near the pots point to wet soil. My post on fungus gnats in houseplants explains the fix.

How to wake geraniums up in spring

Start about eight weeks before your last frost date. Count back from that date on the calendar.

For bare-root plants, trim off dead roots and stems. Pot each plant in fresh mix, water it, and set it in bright light. New leaves show up in a couple of weeks. For plants kept in pots, cut back leggy stems to a few inches above a leaf node. This makes the plant branch. Begin feeding with a half-strength fertilizer once new growth starts.

Harden off every plant before it goes outside. Set it out for a few hours a day, then lengthen the time over about a week. My guide on how to harden off seedlings covers the steps. The same routine works for geraniums. Plant them out after the last frost, when nights stay above 50°F (10°C).

Clean your pots and tools before you reuse them. My post on cleaning and storing garden tools for winter has a simple routine.