Rhubarb is a distinct, large-leaved plant often cultivated in home gardens. Although botanically classified as a vegetable, its edible stalks are typically used in sweet dishes. As an herbaceous perennial, the plant emerges each spring from a thick underground rhizome system, forming an imposing clump of foliage. Its robust appearance makes it a striking feature, often reaching heights and widths of over three feet. The plant is extremely hardy and requires a period of cold temperatures (vernalization) to thrive and remain productive for many years.
The Defining Feature: Stalks and Petioles
The most recognized component of the rhubarb plant is the thick, fleshy leaf stalk, or petiole, which is the only part of the plant considered safe to eat. These petioles emerge directly from the central crown in a celery-like structure, often growing up to 18 inches long and one to two inches in diameter. Their surface is typically glossy and can display subtle grooving or ribbing along the length, contributing to their crisp texture.
The color of the edible stalks varies widely depending on the specific cultivar, ranging from crimson red to speckled pink or pure light green. Although red varieties are often preferred for appearance, color is not a reliable indicator of sweetness, flavor, or ripeness; green varieties like ‘Victoria’ are equally desirable for cooking. The leaf stalks are tart due to malic and oxalic acid, necessitating the addition of sugar for most culinary uses.
Leaf Structure and Appearance
Rhubarb leaves are massive and dramatic, forming a dense canopy above the ground. The leaf blades are held high by the petioles and are generally triangular or heart-shaped, sometimes growing to an impressive two feet across. The surface of the blade is a deep, dull green and is characterized by a crinkled or wavy texture with very prominent veins radiating from the point where it connects to the stalk.
The large size and deep green color of the leaves indicate the plant’s robust photosynthetic capacity. However, the leaves contain high concentrations of oxalic acid, making them toxic and inedible for human and animal consumption. While oxalic acid is present throughout the plant, the leaves contain significantly more (0.5–1.0% of the leaf mass), so the leaf blade must be completely removed before the stalk is prepared for eating.
Seasonal Growth and Flowering
Rhubarb is one of the first plants to show signs of life in the spring, with reddish buds pushing through the soil as temperatures rise. The plant rapidly grows into a substantial clump, reaching its full size of two to four feet in height and width by late spring. This initial vegetative growth is focused on producing the large leaves and thick, harvestable petioles.
As the season progresses, mature plants may occasionally “bolt,” producing a tall, thick flower stalk from the center of the crown. This stalk is distinct from the leaf petioles; it is hollow and topped with large, branched clusters of small, creamy white or greenish-white flowers. Gardeners typically remove these stalks immediately because flowering diverts the plant’s energy away from producing edible petioles.
Distinguishing Rhubarb from Toxic Look-Alikes
Rhubarb’s appearance is sometimes confused with other plants, necessitating careful visual inspection before harvesting.
Burdock
One common look-alike is Burdock (Arctium species), sometimes called “wild rhubarb,” which also has large leaves and reddish stems. The primary difference is that Burdock leaves are typically covered in fine fuzz or hair, whereas true rhubarb leaves are smooth.
Pokeweed and Skunk Cabbage
Pokeweed (Phytolacca decandra) is another plant sometimes confused with rhubarb, featuring a central red stem. Unlike rhubarb, which grows as a cluster of stalks from a central crown, Pokeweed has a single main stem, and its leaves are much narrower and lighter green. Skunk Cabbage (Symplocarpus foetidus) can resemble rhubarb in early growth, but it is found exclusively in marshy or boggy areas, a habitat rhubarb avoids, and lacks the distinctive coloration of rhubarb petioles.