Unraveling Rhubarb's Botanical Mystery
Most people associate rhubarb with sweet pies, jams, and other desserts, a culinary role that has led many to assume it is a fruit. This is a common misconception, so much so that a 1947 U.S. court ruling actually classified it as a fruit for tariff purposes. However, botanically, rhubarb is an herbaceous perennial vegetable. Its true identity lies in its family tree, revealing unexpected relationships with other plants.
The Surprising Link to the Buckwheat Family
The primary vegetable that is related to rhubarb is buckwheat, alongside sorrel and dock. All these plants are members of the Polygonaceae family, often referred to as the knotweed or buckwheat family. This family's name, Polygonaceae, comes from the Greek words 'poly' (many) and 'gonu' (knee), referencing the distinct, swollen joints or nodes on the stems of many of its members. Despite looking nothing like a traditional grain, buckwheat is also a member of this family, and its seeds are used in a similar way to cereals, hence its classification as a pseudo-cereal. Understanding this shared lineage helps clarify rhubarb's botanical roots and its distinction from fruits.
More Relatives: Sorrel and Dock
Beyond buckwheat, other lesser-known relatives of rhubarb include sorrel and dock. Both are also members of the Polygonaceae family. Sorrel is a leafy green herb with a bright, lemony flavor that is used in salads, soups, and sauces. Dock, on the other hand, is a more common wild plant, often considered a weed, though its leaves are sometimes used in cooking, similar to sorrel. These relationships highlight the diversity within the Polygonaceae family, which ranges from tart-stalked vegetables to leafy greens and pseudo-cereals.
Edible Stalks vs. Poisonous Leaves
A critical point of differentiation for rhubarb, even within its own family, is its toxicity. While the stalks (or petioles) are edible, the leaves are poisonous. The leaves contain high levels of oxalic acid, a chemical compound that can cause serious illness and kidney problems if ingested in large quantities. This is why rhubarb is typically sold with the leaves removed. Fortunately, the stalks contain much lower concentrations of oxalic acid, making them safe to eat, especially when cooked. This toxicity contrast is a key feature to remember when harvesting or preparing rhubarb.
Culinary Differences and Similarities
Despite their shared botanical family, rhubarb and buckwheat serve vastly different culinary purposes. Rhubarb is known for its intense tartness and fibrous stalks, which are almost always sweetened and cooked for use in desserts, compotes, and jams. Buckwheat, meanwhile, is prized for its nutty flavor and gluten-free seeds, used to make flour, groats, and noodles. This stark divergence in culinary application is a perfect example of how members of the same family can evolve to serve different dietary roles.
Authoritative Resource on Rhubarb
For those interested in learning more about the cultivation and science of rhubarb, the Michigan State University Extension provides valuable, research-based information. Their resources offer insights into growing conditions, varieties, and the plant's nutritional benefits, further emphasizing its status as a nutrient-packed vegetable rather than a fruit.
Comparison of Rhubarb, Buckwheat, and Sorrel
| Feature | Rhubarb (Rheum rhabarbarum) | Buckwheat (Fagopyrum esculentum) | Sorrel (Rumex acetosa) |
|---|---|---|---|
| Botanical Family | Polygonaceae | Polygonaceae | Polygonaceae |
| Edible Part | Tart stalks (petioles) | Seeds, used as a pseudo-cereal | Leaves, used as an herb |
| Taste Profile | Very tart and sour | Nutty, earthy | Bright, lemony |
| Culinary Use | Desserts, pies, jams (often sweetened) | Flour, groats, noodles | Soups, sauces, salads |
| Toxic Parts | Leaves contain oxalic acid | None (seeds are gluten-free) | Leaves are safe, though high consumption of some varieties is not recommended |
Culinary Versatility of Rhubarb
While most recipes call for sugar to balance rhubarb's tartness, its culinary applications are diverse. Lists of common uses include:
- Pies and Crumbles: Classic desserts, often paired with sweet fruits like strawberries to create a balanced flavor.
- Jams and Preserves: The natural pectin in rhubarb makes it excellent for jams, and the acidity helps brighten other fruit flavors.
- Compotes: Simple stewed rhubarb can be served over ice cream, yogurt, or pancakes.
- Sauces for Meats: Its tartness pairs surprisingly well with savory dishes, such as pork or chicken.
- Cocktails and Syrups: Rhubarb can be cooked into a syrup for use in cocktails, spritzers, or lemonade.
Growing Rhubarb at Home
Rhubarb is a hardy perennial that is relatively easy to grow, particularly in cooler climates. Here are some tips for success:
- Site Selection: Choose a sunny to partially shaded location with well-drained, fertile soil.
- Planting: Rhubarb is often grown from root divisions, called crowns, planted in early spring.
- Harvesting: Do not harvest during the first year of growth. In subsequent years, harvest stalks in spring and early summer.
- Fertilizing: Apply compost or a balanced fertilizer annually.
- Care: Keep plants well-watered and free of weeds.
Conclusion: The Buckwheat Family's Unique Member
Ultimately, understanding the vegetable related to rhubarb demystifies its botanical identity. Far from being a fruit, rhubarb is a fascinating perennial vegetable with a close family tie to buckwheat, sorrel, and dock, all belonging to the Polygonaceae family. While its tart stalks are used like a fruit in the kitchen, its botanical classification and its relationship to other plants highlight the unique and sometimes surprising connections found within the plant kingdom. So next time you enjoy a piece of rhubarb pie, remember its unassuming relatives in the buckwheat family that help define its place in the world of plants.
