Geraniums and petunias are such a staple in our gardens that it’s easy to forget they aren’t actually locals. These gorgeous bloomers actually hail from the warm climates of Southeast Africa! Because of those tropical roots, it’s no surprise that frost is basically their worst enemy.
Geraniums and Frost Just Don’t Mix
When it comes to geraniums, the thermometer is your best friend. These plants can’t handle temperatures below freezing; even a quick dip into a light frost can be fatal. Even temperatures consistently below 50°F (10°C) during their blooming season can be a problem, often causing the plant to stop flowering altogether. Because of this, a geranium’s life is usually split into two distinct phases.
The first phase lasts about six frost-free months, where the geranium gets to live its best life outdoors, growing and blooming. The second phase, which also lasts about six months, is a mandatory “nap time” where the plant needs to be tucked away safely from the cold.
The Outdoor Season
In many regions, late spring frosts can linger until mid-May (around the time of the “Ice Saints”). Your geraniums aren’t truly safe until those final cold snaps have passed. It’s best to wait until then before moving them outside or planting them in the ground. Don’t let those first warm spring days fool you—the nights can still get biting cold! If you’re itching to get started, you can set them out for a few hours during the day starting in April, but make sure to bring them back inside before the sun goes down.
Your geraniums can usually stay on the balcony or patio until October. If you’re lucky enough to have a mild autumn, they can stay out a bit longer, but keep a very close eye on the weather forecast and your outdoor thermometer.
Winter Dormancy
The winter phase begins as soon as the first frost is predicted. That’s your cue to move them into winter quarters that are bright but cool—ideally between 40°F and 50°F (5-10°C). A basement with a window is often a perfect spot. Avoid places that are too warm or dark; this can trick the plant into sprouting too early, resulting in weak, spindly growth and fewer flowers next summer.
How to Store Your Geraniums for Winter
Luckily, geraniums are pretty flexible when it comes to their winter housing. You can store them:
- Right in their window boxes with the soil
- Bare-root (dug up with the soil removed)
- Wrapped in newspaper
- Hanging upside down
Pro Tip:
Give your geraniums a heavy pruning before moving them into storage. Once winter is over and it’s time to wake them up, that’s the perfect moment to repot them into some fresh, nutrient-rich soil.
Can You Overwinter Geraniums Outside?
If you don’t have a good indoor spot but you do have a garden, you can try an old-school overwintering trick:
- Dig a pit about 30 inches (80 cm) deep.
- Line the bottom with a thick layer of dry leaves.
- Prune your geraniums back and place them inside.
- Cover the pit well to insulate them from the surface cold.
