The question of whether a geranium is an annual or a perennial is a common point of confusion in gardening. The answer depends entirely on which of the two distinct plants you are referencing, as both are widely sold under the same common name. This simple name mix-up dictates whether a gardener should expect the plant to return next spring or be replaced. Understanding the difference is key to successful planting and care.
Understanding the Name Confusion
The confusion stems from a historical botanical error involving two separate genera within the Geraniaceae family. The plant most people buy for summer window boxes and bedding displays belongs to the genus Pelargonium. These common bedding “geraniums” feature large, showy flower clusters and often have a distinctive scent.
The true perennial garden plant belongs to the genus Geranium, often called “cranesbill” or “hardy geranium.” Both were originally classified together by Carl Linnaeus but were separated into two distinct genera in 1789 due to differences in their flower structure and seed capsules.
Cranesbills have five uniform petals, creating a radially symmetrical flower. Conversely, Pelargonium flowers are asymmetrical, with the two upper petals typically differing from the three lower petals. Despite the reclassification, the common name “geranium” stuck to the more popular Pelargonium, causing continued confusion.
Why Common Garden Geraniums Are Annuals
The common bedding plants, Pelargoniums, are technically classified as “tender perennials.” They are native to the warm, dry climates of South Africa, adapting them to year-round growth. While their succulent stems and leaves withstand drought and heat, they have a very low tolerance for cold.
Temperatures consistently below 40 degrees Fahrenheit or even a light frost will cause significant damage or death. Consequently, in most temperate regions, Pelargoniums cannot survive the winter outdoors. They are only truly perennial in USDA Zones 9 through 11, where the climate remains warm enough for them to thrive year after year.
Outside of these mild areas, the plants must be replanted every spring, making them function as annuals. Their inability to withstand winter cold is the defining factor that determines their status as annuals for the average gardener.
The Reliable Perennial Geraniums
The true Geranium species, or cranesbills, are the reliable perennial option. These plants are built for cooler climates, with many varieties exhibiting excellent cold hardiness, surviving temperatures down to USDA Zone 3 or 4. Unlike their tender cousins, these plants enter a state of winter dormancy, allowing them to withstand harsh, prolonged freezes.
They are herbaceous perennials, meaning their above-ground growth dies back completely each fall. Energy is stored in the root crown, and new foliage emerges vigorously once spring temperatures rise. This robust life cycle allows them to return reliably for many years, acting as durable groundcovers or border fillers.
Over 700 varieties of cranesbills exist, offering a wide range of colors and growth habits. They are generally low-maintenance, requiring only a cutback to the ground level once the foliage fades in late autumn.
Keeping Tender Geraniums Alive Year After Year
Gardeners who wish to save their favorite Pelargonium plants from winter can transform them from annuals into true perennials through overwintering. There are three primary methods for achieving this:
Temporary Houseplant
This is the most common method. Before the first frost, plants should be dug up, potted into a container, and placed in a bright, sunny window. During the winter, the plant should be kept cool, ideally between 60 and 65 degrees Fahrenheit, and watered sparingly only when the soil surface feels dry.
Taking Cuttings
A space-saving technique is to take cuttings from the main plant in late summer. These small stem sections are rooted in a sterile medium. Cuttings require less space and light than a full-sized plant.
Bare-Root Dormancy
This hands-off method involves storing the plant bare-root in a dormant state. The plant is dug up before the frost, the soil is shaken off the roots, and the plant is hung upside down or placed in a paper bag in a dark, cool location that remains above freezing, such as a cool basement. This storage area should maintain a temperature between 45 and 55 degrees Fahrenheit. Plants should be left mostly dry until they are repotted and watered again in early spring.