The most striking difference lies in their fundamental architecture. Zonal geraniums (Pelargonium × hortorum) exhibit a sturdy, upright growth habit. They develop thick, succulent-like stems that stand erect, forming a mound of foliage and flowers that typically reaches heights of 1 to 3 feet. In contrast, Ivy geraniums (Pelargonium peltatum) are true trailing plants. They possess long, slender, and flexible stems that can cascade gracefully over the edges of containers and hanging baskets, often reaching lengths of 3 to 5 feet. This vining nature is their defining characteristic.
The leaves of these two plants provide an easy way to tell them apart. Zonal geraniums bear rounded, softly lobed leaves that are often slightly ruffled and have a velvety texture. Their common name originates from the prominent, horseshoe-shaped "zone" or band of darker color—often bronze, purple, or maroon—that circles the center of the leaf. The foliage has a distinct, pungent scent when brushed. Ivy geranium leaves are entirely different; they are glossy, waxy, and smooth to the touch, closely resembling the leaves of true ivy (Hedera helix). They are typically five-lobed, star-shaped, and lack any zonal pattern, being a solid green, though some variegated cultivars exist.
Both produce large, showy flower heads, but the structure and presentation vary. Zonal geraniums produce stout, upright stems that terminate in large, spherical clusters (umbels) of tightly packed, individual flowers. Each flower is typically single or double, but they are held together in a dense, ball-shaped formation well above the foliage. Ivy geraniums also flower in umbels, but the individual flower stems (pedicels) are longer, giving the cluster a looser, more open appearance. The flower clusters are often smaller than those of zonals but are produced in greater profusion along the trailing stems. The individual flowers of ivy types are often slightly asymmetrical, with the upper two petals frequently displaying stronger veining or marking.
While both thrive in full sun and well-draining soil, their performance under certain conditions differs. Zonal geraniums are exceptionally heat-tolerant and can handle drier conditions quite well due to their thicker stems. They are the classic choice for sunny garden beds and container gardens where an upright element is desired. Ivy geraniums, while also sun-loving, are less tolerant of extreme heat and prolonged drought. Their thinner stems and leaves lose water more readily. They excel in hanging baskets, window boxes, and elevated planters where their trailing habit can be showcased, and they often perform better than zonals in slightly cooler summer climates.
