How to Overwinter Geraniums So They Thrive in the Summer, According to Horticulturists

Geraniums are one of summer's most beloved blooms. These beautiful blossoms can bathe your garden in a sea of bright pink, purple, orange, and lavender—the perfect showy display for the warmer months.

Geraniums are perennials and thrive in full sun. So when the wintertime rolls around, they'll quickly die out if they aren't protected. The good news is that you can overwinter these plants, keeping them safe from the frost and replanting them in the garden when warmer temps finally return. Here, we spoke to gardening experts about how to overwinter your favorite geraniums so they'll thrive for many seasons to come.

When to Overwinter

Timing is key when it comes to overwintering. If you leave flowers out for too long, then they'll succumb to frost, but taking them inside too early can inhibit growth.

It's especially important to properly overwinter geraniums, because these plants are native to South Africa, where they get plenty of sun. According to Mike Kingten, curator of alpine collections at the Denver Botanic Gardens, the best time to bring geraniums inside is just before the first frost.

"Geraniums like cool and bright conditions," he adds. "Houses are often dark and warm. The less time geraniums spend inside, the better."

How to Overwinter

Geraniums need special care when inside during the winter months. Even the place you choose to overwinter them is important.

Find Light

Since geraniums need full sun, light is one of the most critical things to consider when it comes to overwintering. Shauna Moore, director of horticulture at the Brooklyn Botanic Garden, recommends placing your geraniums near a big, south-facing window that gets plenty of sun. However: "The very best place for them is in a greenhouse or conservatory," she adds.

Keep It Cool

Your overwintered geraniums will do best in a cool environment that's about 50 to 60 degrees Fahrenheit. Not only is this the ideal climate for the plant, but it will also help deter pests like whiteflies, aphids, and mealybugs.

Cut Back

Outdoor geraniums will be quite leggy when you move them indoors, so cutting back is an important step in the overwintering process. "I cut back leggy stems and clean up dead leaves and spent flower clusters," says Kingten. "If the plant is very leggy, I give it a hard cutback."

Mistakes to Avoid

One of the most common mistakes people make when overwintering geraniums is watering them incorrectly. "When the days are shorter and there's less sunlight, plants require less water," says Moore. "Geraniums, in particular, benefit from a lighter touch when watering."

Kingten agrees, noting that he lets his geraniums dry out between waterings almost to the point of wilting. He recommends watering them once a week, as overwatering can lead to root rot.

Another common dilemma is not giving your geraniums enough light. If the natural light in your home isn't cutting it—and you don't have a greenhouse on hand—then grow lights are a great solution.