The question of whether Rheum rhaponticum is edible is not a simple yes or no; the answer depends entirely on which part of the plant you are considering. Also known as rhapontic or false rhubarb, this species is a wild relative of the common garden rhubarb and carries the same crucial distinction between its safe stalks and its dangerous leaves. Consuming the wrong part can lead to severe health issues due to high levels of a toxic compound. This guide provides a detailed look at the edible and inedible components, as well as the historical context and modern uses of this intriguing plant.
Understanding Rheum rhaponticum: The Edible and Toxic Parts
The Edible Stalks (Petioles)
Like other members of the Rheum genus, the fleshy stalks or petioles of Rheum rhaponticum are perfectly safe and edible. These stalks have a tart, acidic flavor and are commonly used in desserts like pies, jams, and crumbles, much like their domesticated cousin. The edible portion can be prepared raw or cooked, with cooking often used to mellow the strong, acidic flavor. The young flower pouches, harvested before the flowers fully open, are also considered a delicacy by some.
The Poisonous Leaves
The large, triangular leaves of Rheum rhaponticum, however, are highly poisonous. Their toxicity is primarily due to a high concentration of oxalic acid, a substance that can cause serious illness and, in rare cases, be fatal. Ingesting the leaves can lead to a range of symptoms, from mild stomach upset to more severe health problems. For this reason, it is imperative to remove and discard the leaves immediately after harvesting the stalks, ensuring they are not mistakenly prepared for consumption.
The Medicinal Roots
Historically, the roots of various Rheum species, including R. rhaponticum, have been used in traditional medicine for a variety of purposes. Rhapontic rhubarb root is particularly noted for its use in supplements designed to relieve menopausal symptoms. The root contains phytoestrogenic compounds, such as rhaponticin, which have shown potential benefits in reducing hot flashes and other discomforts. However, this medicinal use is distinct from culinary consumption and involves standardized extracts rather than consuming the raw root, which also contains other potent compounds.
Rheum rhaponticum vs. Common Garden Rhubarb
While most people are familiar with the bright red stalks of cultivated rhubarb (Rheum x hybridum or Rheum rhabarbarum), R. rhaponticum is a wild species with some key differences.
| Feature | Rheum rhaponticum (Rhapontic Rhubarb) | Rheum x hybridum (Garden Rhubarb) |
|---|---|---|
| Origin | Native to Europe and Siberia. | Cultivated hybrid, developed from several Rheum species. |
| Growth Habit | Robust perennial, can grow larger in the wild. | Generally cultivated in gardens and allotments. |
| Appearance | Wild forms may have greener, looser flower panicles. | Common varieties often have intense red stalks and smaller flowers. |
| Genetics | Wild species, often diploid with 2n=22 chromosomes. | Modern cultivars are typically tetraploid with 2n=44 chromosomes. |
| Edible Parts | Stalks only; leaves are toxic. | Stalks only; leaves are toxic. |
| Historical Use | One of the first rhubarb species seen by Europeans, used medicinally. | Became a popular culinary vegetable in the 18th century. |
How to Safely Harvest and Prepare Rhapontic Rhubarb
Proper Harvesting Techniques
When harvesting any rhubarb, including Rheum rhaponticum, it is crucial to handle the plant correctly to ensure safety. The recommended method is to pull or twist the stalk from the base rather than cutting it. This prevents leaving a stub on the plant that could rot and attract pests or diseases. Additionally, harvesting should not exceed one-third of the plant's stalks at a time to maintain its health and future growth.
Preparing the Stalks
The preparation process is straightforward. First, wash the stalks thoroughly under cold water. Next, chop the stalks into smaller pieces suitable for your recipe, typically used in cooked dishes that balance the tart flavor with sweeteners. If you notice any fibrous strands on the outer part of the stalk, you can peel these away, especially for younger, more tender stalks.
Potential Health Risks and Considerations
While the stalks are safe in moderation, excessive consumption can pose risks, especially for certain individuals.
- Oxalic Acid: Even the edible stalks contain some oxalic acid, though at much lower levels than the leaves. For most people, this is not an issue, but individuals with a history of kidney stones, gout, or related conditions should exercise caution, as oxalic acid can aggravate these problems.
- Laxative Effects: Rhubarb, particularly the roots and stems, contains anthraquinone derivatives that have a laxative effect. Large amounts of rhubarb can cause diarrhea, cramps, and other gastrointestinal distress, especially when used medicinally.
- Drug Interactions: Rhubarb can interact with certain medications, such as digoxin, corticosteroids, and blood thinners. Always consult a healthcare provider if you are on medication and plan to consume rhubarb in medicinal amounts.
Conclusion
In summary, you can eat Rheum rhaponticum, but only the stalks. The leaves are toxic due to their high oxalic acid content and must never be consumed. It is vital to correctly identify the edible parts, harvest the stalks safely by pulling them, and discard the leaves completely. While the stalks are a flavorful addition to many culinary dishes, the roots are used in controlled medicinal supplements for menopausal symptoms and should not be self-prescribed. By understanding the specific edible and toxic parts, you can safely enjoy this ancient plant while avoiding any potential harm. Individuals with certain health conditions or those taking specific medications should be especially cautious and seek medical advice before consuming rhubarb.
