The survival of a geranium outdoors in winter depends entirely on its botanical classification and the specific climate conditions. Most people are familiar with the brightly colored plants sold in garden centers, used in window boxes and hanging baskets throughout the summer. These popular flowers are extremely sensitive to cold and cannot tolerate frost, meaning they will not survive the outdoor winter temperatures of most regions.
The Critical Distinction: Hardy vs. Tender Geraniums
The plant most often called a “geranium” is botanically classified as a Pelargonium, which is a tender perennial. These species, including the Zonal, Ivy, and Scented types, originated in South Africa. They possess succulent stems that turn to mush when subjected to freezing temperatures, necessitating protection or replacement each year.
The true, hardy perennial geranium belongs to the genus Geranium and is commonly known as Cranesbill, named for the resemblance of its seed capsule to a crane’s bill. These plants are native to temperate regions and are built to survive cold, dormant periods. Unlike their tender cousins, true Geraniums are highly resilient perennials that return year after year.
Geographic Factors in Winter Survival
Local geography and temperature extremes are the primary factors dictating a geranium’s chances of survival. The USDA Plant Hardiness Zone system categorizes regions based on their average annual minimum winter temperature. Tender Pelargoniums can only survive outdoors year-round in zones 9, 10, and 11, where temperatures rarely fall below freezing.
In contrast, true Geranium species exhibit a much greater tolerance for cold, with many varieties surviving in zones as low as 4 or 5. These hardy plants require a period of cold dormancy to thrive and can withstand prolonged freezing temperatures and snow cover. For gardeners in zones below 9, leaving a tender Pelargonium outside will result in its death.
Protecting Tender Varieties During Dormancy
For the tender Pelargoniums that cannot tolerate frost, there are several practical methods to ensure they survive the winter indoors. One common approach is treating the plant as a temporary houseplant. Before the first hard frost, the plants are pruned back by about one-third to one-half of their size. They are then moved to a cool, brightly lit location, such as a south-facing window. During this semi-dormant period, they require less frequent watering and no fertilizer, with ideal temperatures resting around 60 to 65°F.
Another method involves storing the plants in a completely dormant state without soil. The plants are dug up, the excess soil is shaken off the roots, and they are hung upside down or placed in a paper bag. This storage area, often a basement or garage, should maintain a temperature between 45 and 55°F to prevent both freezing and premature growth. The roots must be checked occasionally and lightly misted if they become too shriveled, but otherwise they are left undisturbed until spring.
A third option is taking cuttings from the parent plant before the cold weather arrives. This method saves space and provides fresh, vigorous plants for the next season. Three to four-inch stem tips are cut just below a leaf node, dipped in a rooting hormone, and then placed in a well-draining rooting medium like perlite or sand. These small cuttings are kept in a bright, warm location. Once they develop a robust root system, they are potted up and maintained as small houseplants until they can be safely moved outdoors after the last spring frost.