While both commonly referred to as geraniums, Zonal and Ivy geraniums belong to the same genus, Pelargonium, but are distinct species with different genetic backgrounds. The Zonal geranium, known scientifically as Pelargonium × hortorum, is a complex hybrid, primarily derived from Pelargonium inquinans and Pelargonium zonale. Its name "Zonal" refers to the horseshoe-shaped, dark marking—the zone—found on the leaf. In contrast, the Ivy geranium is Pelargonium peltatum, a distinct species named for its ivy-shaped leaves (peltatum meaning shield-shaped, referring to how the leaf stalk attaches to the center of the leaf blade). This fundamental genetic difference is the root of all their subsequent variations in form and habit.
The most striking difference from a horticultural perspective is their growth habit. Zonal geraniums exhibit a upright, erect growth pattern. They develop thick, succulent-like stems that grow vertically, creating a mounded, bushy plant ideal for containers and garden beds where upward growth is desired. Conversely, Ivy geraniums are true trailing plants. They possess long, slender, and flexible stems that cascade gracefully over the edges of containers, hanging baskets, and walls. This vining habit is a key adaptive trait, allowing them to spread and cover ground in their native habitats.
The foliage of these two plants provides an easy visual identifier. Zonal geranium leaves are orbicular (roundish) to kidney-shaped with a velvety texture due to fine hairs. They are typically soft, slightly fuzzy to the touch, and often emit a distinct pungent scent when crushed. The aforementioned dark zonal band is a common, though not universal, feature. Ivy geranium leaves are entirely different; they are glossy, waxy, and smooth (glabrous). Their shape is distinctly ivy-like—lobed, angular, and leathery—an adaptation that helps reduce water loss. They lack the strong scent characteristic of their zonal cousins and do not have a zonal band.
Both plants produce large, showy flower heads (umbels), but the presentation differs. Zonal geraniums hold their large, spherical flower clusters proudly atop stiff, upright stems that rise well above the canopy of foliage. The individual flowers are often larger and can be single, double, or even rosebud-like in form. Ivy geraniums, with their trailing nature, produce flower clusters that are more lax and tend to emerge from the stems, often hanging below the level of the foliage. The individual flowers are generally smaller and more numerous per cluster, and they are most commonly single or semi-double, with a appearance that is often described as more delicate.
