The question of whether geraniums are annuals or perennials is a common point of confusion for gardeners. The simple answer is that they can be both, depending entirely on the specific plant referenced. This ambiguity arises because two different genera of plants are commonly sold under the single name “geranium.” Understanding the botanical distinction determines a plant’s true life cycle and whether it will return next season.
Understanding the Geranium Identity Crisis
The confusion surrounding the geranium’s life cycle stems from a centuries-old classification error. Both the perennial and annual plants belong to the same family, Geraniaceae, but they are members of two distinct genera. The Swedish botanist Carl Linnaeus initially grouped all these related species into the genus Geranium in the 18th century.
In 1789, botanists recognized significant differences in their flower structure and seed capsules, leading to a separation into two genera. The showier, frost-tender plants were moved to the genus Pelargonium, while the hardier ones retained the name Geranium. Despite this scientific correction, the common name “geranium” stuck to both groups, causing the persistent identity crisis today.
True Geraniums (The Perennial Answer)
The plants botanically classified as true geraniums belong to the genus Geranium and are considered hardy perennials. They are often called Cranesbill, a reference to their long, beak-like seed pods. True geraniums are native to temperate regions of Europe and North America and are adapted to survive cold winters.
Cranesbills are hardy in USDA Zones 3 through 9, reliably returning year after year in most temperate climates. They possess a low, mounding or spreading growth habit, making them excellent ground covers or border fillers. Their flowers usually have five equal-sized petals and are smaller than their annual counterparts, appearing in shades of blue, purple, pink, or white.
These herbaceous perennials die back to the ground after the first hard frost and emerge again from their root structure in the spring. Many varieties, such as Geranium ‘Rozanne’, are known for their extended bloom period and ability to tolerate a wide range of soil conditions. Their foliage is often lobed or dissected, and some species develop attractive fall color.
Common Geraniums (The Annual Answer)
The bright, showy plants found in hanging baskets and patio planters are common geraniums, belonging to the genus Pelargonium. These plants are native to the warm, arid regions of Southern Africa, where they grow as evergreen perennials. Because they originate from a frost-free climate, they are classified as tender perennials or half-hardy annuals.
In most of North America and Europe, which fall outside their native hardiness zones of 10 and 11, Pelargoniums cannot survive freezing temperatures. Gardeners treat them as annuals, expecting them to thrive for a single season before being replaced the following spring. Common types include Zonal geraniums, named for the horseshoe-shaped pattern on their leaves, Ivy geraniums with their trailing habit, and Regal or Martha Washington geraniums.
Pelargonium flowers are distinct because they are arranged in dense clusters, and the five petals are often unequal in size, creating a less symmetrical appearance than a true geranium. These plants are prized for their long blooming season, producing vibrant flowers in colors like scarlet, salmon, and orange. Their stems tend to become woody over time, a characteristic of their perennial nature in warmer climates.
Extending the Life of Common Geraniums
While common geraniums are treated as annuals, gardeners in colder climates can keep their plants for multiple seasons through overwintering. This process must be completed before the first frost, as Pelargoniums are highly susceptible to cold damage. The two popular methods involve either bringing the plants indoors to grow actively or forcing them into dormancy.
Overwintering as Houseplants
To overwinter plants as houseplants, pot up garden specimens in fresh soil and place them in a bright location, such as a south-facing window. The temperature should remain consistently above 40 degrees Fahrenheit. Water them sparingly, allowing the soil to dry out between waterings. Inspecting the plant for pests and disease and pruning them back slightly before bringing them inside ensures a healthy transition.
Bare-Root Storage
The second method is bare-root storage, which forces the plant into a dormant state in a cool, dark, and dry environment. Plants are dug up, the soil is gently shaken off the roots, and the foliage and stems are pruned back. The bare-root plants can then be hung upside down or placed in paper bags in a frost-free location. This location, such as a cool basement or garage, should maintain temperatures between 40 and 60 degrees Fahrenheit. These dormant plants require no water during the winter but should be checked periodically for signs of desiccation or rot.