Rheum, commonly known as rhubarb, is a genus of robust perennial plants that belong to the family Polygonaceae. Often grown for both ornamental and culinary uses, the rheum plant is known for its thick stalks, large leaves, and vibrant red or green stems. While the leaves of the plant are toxic due to their oxalic acid content, the stalks are popular in cooking, especially for making pies, jams, and sauces. Beyond culinary value, certain types of rheum are prized in traditional medicine for their therapeutic properties. Understanding the different types of rheum plants helps gardeners, herbalists, and chefs alike select the right variety for their specific needs.
Overview of Rheum Genus
Botanical Characteristics
Rheum plants typically feature large, heart-shaped or triangular leaves with pronounced veining. Their hollow stalks, or petioles, are thick and juicy, often exhibiting red or green hues. These plants can reach up to two meters in height and thrive in temperate climates. The flowers are usually small and clustered in large, upright inflorescences, often white, pink, or greenish in color.
Habitat and Cultivation
Native to Asia, particularly the mountainous regions of China, Tibet, and the Himalayas, rheum plants have spread across Europe and North America. They prefer well-drained, fertile soils and require a dormant winter period for optimal growth. While some types are cultivated for ornamental beauty, others are specifically grown for culinary or medicinal purposes.
Common Types of Rheum Plant
Rheum rhabarbarum (Garden Rhubarb)
This is the most widely cultivated variety used in culinary applications. Garden rhubarb features thick red or green stalks that are tart and used in various recipes. There are many cultivars within this category, each differing slightly in color, taste, and harvest time.
- Victoria: A traditional variety with green stalks tinged with pink, known for its large yields and reliable growth.
- Canada Red: Shorter stalks with a sweeter taste and deep red color, excellent for pies and preserves.
- Timperley Early: One of the earliest varieties to harvest, with slender red stalks and a mild flavor.
Rheum officinale (Chinese Rhubarb)
Rheum officinale is primarily grown for medicinal use rather than culinary purposes. The roots of this species are used in traditional Chinese medicine as a purgative and anti-inflammatory agent. It has a robust growth habit and can reach significant heights. The stems are not typically consumed due to their bitterness and strong chemical content.
Rheum palmatum (Turkey Rhubarb)
Also used in traditional medicine, Rheum palmatum is notable for its deeply lobed leaves and impressive size. It is sometimes referred to as Chinese rhubarb as well, which can cause confusion with R. officinale. The roots are used to treat digestive disorders and are often found in powdered or capsule form in herbal shops.
Rheum nobile (Noble Rhubarb)
This unique species is native to the Himalayas and is known for its translucent bracts that protect its flowers from the extreme alpine climate. Rheum nobile is not grown for consumption or medicine but is admired for its striking appearance. It grows in high altitudes and is considered a marvel of alpine flora.
Rheum australe (Himalayan Rhubarb)
Also native to the Himalayan region, Rheum australe is a rare and endangered species used in traditional Tibetan medicine. The plant grows at elevations above 3,000 meters and features large, lobed leaves with reddish veins. It is often confused with other medicinal rhubarbs but is distinguishable by its unique growth habitat and appearance.
Uses of Rheum Varieties
Culinary Applications
Only a few types of rheum are suitable for eating. The edible varieties, especially R. rhabarbarum, are used in sweet and savory dishes alike. The tartness of the stalks pairs well with sugar, strawberries, and citrus fruits. Some common uses include:
- Rhubarb pie and crumble
- Compotes and jams
- Sauces for meats and poultry
- Fermented rhubarb beverages
Medicinal Applications
Several types of rheum are recognized for their health benefits, particularly in traditional medicine systems. The roots of R. officinale and R. palmatum are rich in anthraquinones, which act as natural laxatives. These species are used to treat:
- Constipation
- Detoxification
- Digestive complaints
- Liver conditions
However, these treatments should only be used under professional guidance due to the potency and potential side effects of the compounds involved.
Growing Tips for Rheum Plants
Soil and Sun Requirements
Rheum plants prefer slightly acidic to neutral soils with good organic content. They should be planted in full sun to partial shade. Mulching around the base helps retain moisture and suppress weeds.
Watering and Fertilization
Regular watering is essential, especially during dry spells, but overwatering can lead to root rot. Applying compost or a balanced fertilizer during the growing season will support healthy growth and stalk production.
Harvesting Guidelines
Stalks should only be harvested once the plant is well-established, typically in its second or third year. Harvest by pulling the stalk from the base rather than cutting, which helps reduce the chance of disease. Never eat the leaves, as they contain oxalates that are toxic to humans and animals.
Potential Risks and Toxicity
Leaf Toxicity
All types of rheum plants have poisonous leaves. The high levels of oxalic acid and anthraquinone glycosides can lead to symptoms like nausea, vomiting, and kidney failure if ingested in large amounts. It’s important to discard the leaves safely and keep them away from pets and livestock.
Allergic Reactions
Handling certain rhubarb plants may cause skin irritation in sensitive individuals. Wearing gloves during harvesting and preparation is recommended to avoid any adverse reactions.
The Rheum genus includes a wide range of plant types, from the familiar garden rhubarb to exotic high-altitude species like Rheum nobile. Whether grown for their tart edible stalks, striking ornamental value, or powerful medicinal properties, rheum plants offer a diverse array of benefits. Understanding the specific characteristics of each type such as Rheum rhabarbarum for the kitchen and Rheum officinale for herbal use can help individuals choose the right variety for their garden or practice. With proper care and caution, these versatile plants can be a rewarding addition to both horticultural and health-focused environments.