The similar appearance of rhubarb and celery stalks often leads to confusion about their botanical relationship. Both plants feature long, fleshy, and somewhat stringy petioles, or leaf stalks, that are harvested for culinary use. This visual and structural resemblance raises the question of whether they belong to the same plant group.
Rhubarb and Celery Belong to Different Families
Rhubarb and celery are not closely related and belong to entirely separate plant families. Rhubarb (genus Rheum) is a member of the Polygonaceae family, commonly known as the knotweed or buckwheat family. Celery (Apium graveolens) belongs to the Apiaceae family, also known as the carrot or parsley family. This difference confirms that the two plants share no direct botanical link, despite their superficial similarity. Their structural resemblance is an example of convergent evolution, where unrelated organisms evolve similar traits to suit a similar function, such as supporting a large leaf blade.
Understanding Rhubarb’s Unique Classification
Rhubarb is classified as a perennial herbaceous plant that grows from short, thick rhizomes. The Polygonaceae family is characterized by plants that often have swollen joints or nodes on their stems. Rhubarb’s edible portion is the leaf stalk, or petiole, which is notable for its tart flavor and is used culinarily as a “fruit,” though botanically it is a vegetable. The stalks of the cultivated variety, Rheum × hybridum, can range in color from green to vibrant red.
A characteristic of rhubarb is the toxicity of its large, triangular leaves. The leaf blades contain high concentrations of oxalic acid and anthrone glycosides, making them poisonous and inedible. Ingestion of the leaves can be harmful, and only the fleshy petioles should be consumed. This distinction between the edible stalk and the toxic leaf is important for anyone using rhubarb in cooking.
The Apiaceae Family
Celery is an erect biennial or perennial herb that fits within the Apiaceae family, a large group of plants known for their aromatic properties. This family is also called Umbelliferae because of its defining floral characteristic: the flowers are arranged in a compound umbel. An umbel is a flower cluster where all the stalks radiate from a single point, resembling the spokes of an umbrella.
The Apiaceae family includes many common herbs and vegetables, such as:
- Carrots
- Parsley
- Dill
- Parsnips
- Fennel
These relatives share the family’s distinctive features, including small, radially symmetrical flowers and often hollow stems. The differences in flower structure and other botanical traits between Apiaceae and Polygonaceae establish that celery and rhubarb are classified separately.