During winter, geraniums grow best with night temperatures of 50° to 60°F (10° to 16°C) but will survive if they drop to 32°F (0°C) and/or rise above 80°F (27°C), as long as they are kept relatively dry. When new growth appears in the spring, cut off all the old leaves.
At what temperature should geraniums be brought inside? Once nightly temperatures fall below around 55 degrees Fahrenheit, it's time to bring your geraniums inside if you plan to overwinter them indoors. If they're exposed to frost, it might already be too late to overwinter a healthy plant.
Below 32˚F is considered a freeze, which is more destructive than a frost. Tender plants, such as tropical houseplants and geraniums, are killed when the air temperature stays below 32˚F for a few hours.
Annual geraniums cannot be kept outside in the winter, unless you live in zones 9-12. In all other hardiness zones, containers will need to be brought inside to overwinter. Place containers in a sunny, cool location, such as a west-facing window.
Overwinter geraniums as bare-root plants
Place one or two plants in a large paper sack and store in a cool (45- to 50-degree F), dry location. Or hang the plants upside down in a cool, dry location. The foliage and the shoot tips will eventually die.
If the stems and roots are intact, the plants will regenerate. In late spring it is not worthwhile to protect geraniums from frost.
Annual geraniums (Pelargonium hybrids) are amazing — they grow and bloom beautifully from spring to frost without a lot of fuss. Then you dig them up in fall, put them in a cardboard box or a paper bag to store over winter and these tough little plants will take off and grow again the following spring.
Steps to Overwintering Dormant Geraniums
Transplant the geraniums from the garden into plastic pots or other containers before the first frost, and cut the plant back by about half. Allow the soil in the pot to dry out. Place an overturned paper bag on top of each plant.
The average life expectancy of a geranium is about two years, and although they will last much longer than that, they tend to get woody and the blooms diminish. Luckily, propagation is easy with geraniums. Simply take four-inch stem tip cuttings with at least two pairs of healthy leaves.
If you have room for the pots in a sunny location, you can bring your potted geraniums (Pelargoniums) into your house for the winter. While they need sun, they do best with moderate temperatures 55°-65°F (12°-18°C).
If it stays cold for more than one night, can I keep my plants covered, or should I remove the coverings at some point? A. Our recommendation would be to remove the cold protection covering once temperatures are above 32 degrees.
A covered porch usually provides protection from light frost, but the garage or sun room is better for freezing temperatures. A couple days in darkness won't hurt the plant. Or move them out during the day and back in at night, if cold temperatures persist.
Few flowers look as good in a pot as these do. They blend handsome foliage with large clusters of show-stopping blossoms in colors of red, pink, rose, salmon, orange, lavender, violet, or white. Although many people use geraniums as bedding plants, we think they perform even better in containers.
For the production of geraniums using the "Fast Cropping" technique, night temperatures of 60 to 65 degrees F and day temperatures of 70 to 75 degrees F are best for optimum plant growth.
Light & Temperature: Bright light is essential to keep geraniums in flower throughout the year. South- and west-facing windowsills are the best locations for geraniums, especially during the winter months. If strong, natural light is not available in the home, artificial light is acceptable.
This method does not require a greenhouse, they can be stored in a shed or garage. Dig them up If using this method, before fall, dig them up and shake off all the soil from the roots and let them dry out for a couple of days.
For geraniums stored as dormant plants during the winter, prune off all of the flowers and flower stems, along with about a third of the length of each stem, before you place the plant in its winter home.
Geraniums only need to be kept frost free, so are very economical to overwinter in the greenhouse. However, we do recommend using a heater to ensure temperatures stay above freezing.
After a perennial geranium has spent the season in bloom and begins to die back, you'll want to prune it. This keeps the plant dormant for the winter and also helps it store energy for spring. Depending on your zone, this might need to happen anywhere from August to late October.
Geranium growing as houseplants will also benefit from a spring trim. Pruning plants back to 4-6 inches will encourage thicker more compact growth. Fertilize these plants once the new growth begins. Your plants will be full and ready to bloom in time for the growing season.