Geranium is a popular flowering plant genus, known for its colorful blooms and ease of cultivation in gardens and containers. These plants are a common sight in window boxes, hanging baskets, and flower beds, providing consistent color throughout warmer months. Certain varieties are also valued for their aromatic foliage. This scent has led to the development of a highly prized essential oil used in various health and wellness applications.
The Botanical Identity Crisis
The name “geranium” creates long-standing confusion in horticulture and commerce, stemming from a classification error made centuries ago. In 1753, the botanist Carl Linnaeus grouped both the native European plants and the newly imported South African species into a single genus, Geranium. This initial lumping together of two distinct groups established the common name that persists today, despite later scientific correction.
The plants sold today as “geraniums” are overwhelmingly members of the genus Pelargonium, which was formally separated in 1789. Both genera belong to the same plant family, Geraniaceae, and share a common feature: a long, beak-shaped seed capsule. This seed capsule is what inspired their names; Geranium comes from the Greek word for crane, and Pelargonium comes from the Greek word for stork. The primary distinction is that true Geranium species are mostly hardy perennials, while Pelargonium varieties are tender perennials, grown as annuals in most temperate climates.
Physical Traits and Natural Habitat
The physical characteristics of the two genera differ, particularly in their native habitats and flower structure. True Geranium species, often called cranesbills, are primarily native to the Northern Hemisphere. They are generally herbaceous plants that die back in winter. Their flowers are radially symmetrical, meaning all five petals are identical in shape and size.
In contrast, the Pelargonium genus originated largely in southern Africa. These plants are typically evergreen perennials that thrive in warm temperate and tropical conditions. Pelargonium flowers exhibit a zygomorphic, or bilaterally symmetrical, structure, where the two upper petals are often larger and shaped differently from the three lower petals. Many Pelargonium species also feature fragrant, sometimes fuzzy leaves that release an aroma when touched, a characteristic not commonly found in true Geranium varieties.
Essential Oil and Aromatic Applications
The essential oil marketed as geranium oil is extracted from specific Pelargonium species, most notably Pelargonium graveolens, often called rose geranium. The oil is obtained through steam distillation of the plant’s aerial parts, particularly the leaves and stems. This process yields a yellowish liquid with a strong, rosy, and minty-floral scent.
The oil’s characteristic aroma and diverse applications are due to its complex chemical profile. The primary compounds are geraniol and citronellol, which together can constitute over 60% of the total essential oil content. Geraniol contributes a sweet, floral, and rosy note, while citronellol provides a fresh, slightly lemony scent and is known for its insect-repellent qualities. This blend of compounds gives the oil anti-inflammatory and antimicrobial properties, making it a common ingredient in perfumery, aromatherapy, and skincare formulations.
Cultivation and Gardening Uses
The common Pelargonium varieties, such as zonal and ivy types, are used as bedding plants to provide season-long color in outdoor displays. Because they are tender and cannot tolerate frost, they are treated as annuals in most parts of North America and Europe, planted in spring and removed before the first hard freeze. These varieties perform best in full sun and require well-drained soil, often flourishing in containers and window boxes.
True Geranium species, or cranesbills, are valued by gardeners for their hardiness and use as reliable perennial groundcovers or border plants. They are generally more tolerant of shade than Pelargonium and will return each year, even in colder climates. Scented-leaf Pelargoniums are often placed near pathways or seating areas so that their leaves can be brushed to release their fragrance.