The question of whether geraniums are hardy is complex because the term “hardy” refers to a plant’s ability to withstand cold and frost without protection. Confusion arises because two distinct plant genera are commonly called “geraniums,” and their cold tolerance is drastically different. Answering this requires knowing which plant you are discussing, as one group is treated as an annual and the other is a reliable, cold-tolerant perennial. Understanding this distinction determines the proper winter care for your plants.
The Two Types of “Geraniums” and Their Hardiness Levels
The colorful, brightly-flowered plants used in summer bedding and containers are technically members of the genus Pelargonium. These are the plants most people picture when they hear “geranium,” and they are decidedly not cold hardy. Pelargoniums are native to South Africa and are considered tender perennials, surviving outdoors only in very mild climates (USDA Hardiness Zones 10 and 11). They are highly susceptible to frost damage and perish when temperatures drop below 40°F (4°C).
The true, hardy geraniums belong to the genus Geranium and are often called Cranesbills due to the shape of their seed pods. These plants are true perennials, meaning they return year after year, and they are significantly more cold-tolerant. Many varieties of Cranesbills are hardy down to USDA Zone 5, with some exceptionally tough cultivars surviving in Zone 3. While Pelargoniums are grown for their showy, clustered blooms, Geraniums are valued for their mounding, ground-covering foliage and their symmetrical, five-petaled flowers.
Winter Survival Strategies for Tender Geraniums
Since the popular Pelargoniums cannot withstand frost, they must be brought indoors before the first hard freeze to survive the winter. Gardeners typically choose one of two main methods for overwintering these tender plants.
Overwintering as Houseplants
The first method is to treat them as houseplants, which works best for plants already in pots. Before moving them inside, you should prune the plants back by about one-third and check the foliage and soil thoroughly for pests like whiteflies or spider mites. Once indoors, the plants require a cool, bright location, ideally with temperatures maintained between 60 and 65°F (15 to 18°C). Reduce watering to only when the topsoil feels dry to the touch, as overwatering in winter can lead to root rot. This approach aims to keep the plant actively growing, though it may become “leggy” due to lower light levels.
Dormant, Bare-Root Storage
The second method involves storing the plants in a dormant, bare-root state, which conserves space but is riskier. Before the first frost, the plants are dug up, and the soil is shaken or rinsed from the roots. The plants are then hung upside down in a cool, dark, and dry location, such as a cellar or garage, where temperatures remain consistently between 35 and 45°F (2 to 7°C). This low temperature forces the plant into dormancy, requiring almost no water until they are re-potted in the spring. Once the threat of spring frost has passed, the overwintered plants are gradually reintroduced to the outdoors in a process called hardening off.
Care and Placement for True, Hardy Geraniums
Hardy Cranesbills require minimal intervention to survive the winter. The primary consideration for these perennial plants is proper placement and soil conditions. They thrive in well-drained soil, which is particularly important because standing water in winter can cause their roots to rot, even if the plant is cold-tolerant.
Most varieties of Geranium perform well in full sun to partial shade. For winter preparation, the most common practice is simply to cut back the faded or untidy foliage to the ground in late autumn or early spring. The remaining root structure is fully protected by the soil and does not need heavy mulching in established beds. This simple maintenance ensures the plant’s energy is stored efficiently and encourages a flush of fresh, vigorous growth when spring arrives.