Introduction
Rheum rhabarbarum L. is a perennial plant that is widely cultivated for its edible stalks. Commonly known as rhubarb, it belongs to the family Polygonaceae and is native to central Asia, specifically the regions of Mongolia, Tibet, and northern China.
Appearance
The plant has large, heart-shaped leaves that can grow up to 18 inches long. It produces thick and fleshy stalks that can range in color from deep red to pale green, depending on the cultivar. Rhubarb grows up to 3 feet in height and can spread up to 4 feet in width when mature.
Uses
The primary use of rhubarb is in cooking, particularly baking, where it is used to make pies, tarts, jams, and sauces. It has a tart, sour flavor that complements sweet dishes. The stalks are the only edible part of the plant, as the leaves contain high levels of oxalic acid, which can be toxic if ingested in large quantities. In traditional medicine, rhubarb has been used as a laxative and to remedy various ailments such as fever, inflammation, and infections. However, its medicinal properties have not been scientifically proven, and it is not recommended as a substitute for conventional medicine.
Common Names
The plant is commonly known as rhubarb, although it is sometimes referred to as pie plant, garden rhubarb, or Victoria rhubarb.
Light Requirements for Rheum rhabarbarum L.
Rhubarb requires full sun to grow properly. However, in areas with extremely hot summers, it may benefit from some shade during the hottest part of the day. This can be achieved by planting it where it will receive shade from taller plants or structures during the afternoon hours.
Temperature Requirements for Rheum rhabarbarum L.
Rhubarb is a cold-loving plant and thrives in locations with cool summers. It can survive winter temperatures as low as -40 degrees Fahrenheit, making it a hardy plant that can withstand harsh conditions. Optimal temperatures for growth range from 40 to 75 degrees Fahrenheit, with temperatures above this range causing decreased growth and poor quality produce.
Soil Requirements for Rheum rhabarbarum L.
Rhubarb grows best in well-draining soil that is rich in organic matter. A soil pH between 5.5 to 6.8 is ideal. The soil should be loamy with good moisture retention, but not waterlogged. If the soil is too heavy, it should be amended with organic matter such as garden compost, aged manure, or leaf mold. Rhubarb benefits from a thick layer of mulch, such as straw or leaves, to retain moisture and suppress weeds.
Cultivation Methods
Before planting Rheum rhabarbarum L., it's essential to prepare the soil correctly. They prefer loose, fertile soil that drains well. Additionally, Rhubarb requires adequate sunlight; therefore, it shouldn't be planted in the shade. The best period for planting Rhubarb is in early spring or late autumn when the soil has warmed sufficiently.
Watering Needs
Rhubarb plants require regular watering, particularly during the summer months when the sun is at its hottest. Ensure that the soil is moist, but not waterlogged, to avoid root rot. Generally, it's necessary to water Rhubarb every two weeks, depending on the weather conditions. Water the plant deeply to ensure the water reaches the roots, and avoid watering the leaves and stem.
Fertilization
Rhubarb plants require regular fertilization to promote healthy growth. Apply a balanced fertilizer in spring, shortly after the plant starts growing. It's essential to avoid over-fertilizing the plant, which can harm its growth. Side dress the plants with well-rotted manure every year in the autumn to provide the nutrients required.
Pruning
Prune Rhubarb plants regularly to keep them healthy and productive. Begin by removing the flower stalks to allow the plant to focus its energy on producing more leaves. Cut the leaves from the base, and avoid twisting them off, as this can harm the crown. When the stalks become thin, it's time to divide the plant and plant the new sections. Dividing the plant every five to six years regularly helps maintain the plant's health and productivity.
Propagation of Rheum rhabarbarum L.
Rheum rhabarbarum L., commonly known as rhubarb, is a perennial plant that is propagated mainly through division of the rootstock. This method is the simplest and most efficient means of propagating rhubarb plants, as it ensures that the resulting plants are true-to-type and healthy.
Division of the Rootstock
The best time to divide the rhubarb rootstock is in early spring or late fall, when the plant is dormant. To propagate the plant through this method, dig up the rhubarb clump and gently separate the roots into several sections. Each section should have at least one bud and a portion of the crown attached to it.
Before planting the divided rhubarb sections, prepare the soil by adding compost and other organic matter to improve the soil's fertility. Ideally, the soil should be well-draining and have a pH of 6.0 to 6.8.
Plant the rhubarb sections in early spring or late fall, making sure to set them in the soil at the same depth as they were before. Space the sections at least 3 feet apart, as rhubarb plants can grow up to 5 feet wide.
Seed Propagation
Rhubarb can also be propagated through seed, but this method is less common as it results in plants that are not true-to-type, meaning they may not exhibit the desired characteristics of the parent plant.
To propagate rhubarb from seed, sow the seeds in a seed tray filled with compost or a seed-starting mix in early spring. Cover the seeds with a thin layer of soil and keep the tray in a warm, bright location. Keep the soil moist but not waterlogged to prevent the seeds from rotting.
Once the seedlings have developed at least two leaves, transplant them into individual pots and continue to grow them in a bright, warm location. If growing rhubarb from seed, it may take up to two years before the plant is mature enough to harvest.
Disease Management for Rheum rhabarbarum L.
Like any other plant, Rheum rhabarbarum L. is prone to diseases that can affect its growth, development, and yield. Below are some common diseases that might affect the plant and ways to manage them.
Bacterial diseases
Rheum rhabarbarum L. can be affected by bacterial diseases such as bacterial spot, crown rot, and bacterial stalk rot. To manage these diseases, farmers should use pathogen-free seeds and plant in well-drained soils. They should also ensure proper plant spacing to allow air circulation and reduce leaf wetness. Applying copper-based fungicides can also help in reducing the spread of these diseases.
Fungal diseases
Rheum rhabarbarum L. is susceptible to fungal diseases such as leaf spot, root rot, and powdery mildew. To control these diseases, farmers should avoid overhead irrigation and reduce leaf wetness by watering at the base of the plant. They should also practice crop rotation and remove infected plant debris to reduce the spread of these diseases. Applying fungicides can also be helpful in controlling these diseases.
Viral diseases
Rheum rhabarbarum L. can be affected by viral diseases such as tomato spotted wilt virus and cucumber mosaic virus. To control these diseases, farmers should prevent the transmission by aphids that carry the viruses. Applying insecticides can help in reducing the population of aphids on the plants. Farmers should also use pathogen-free seeds and practice crop rotation.
Pest Management for Rheum rhabarbarum L.
Rheum rhabarbarum L. is also susceptible to pests such as aphids, cutworms, and slugs. Below are some ways to manage these pests.
Aphids
Aphids are small, soft-bodied insects that can infect Rheum rhabarbarum L. To control aphids, farmers should plant pest-resistant varieties and practice crop rotation. They can also apply insecticidal soap or neem oil to the plants to control the population of aphids.
Cutworms
Cutworms are caterpillar larvae that cut the stems of Rheum rhabarbarum L. at the base, causing the plants to wilt and die. To control cutworms, farmers should avoid planting the crop in areas that are infested with the pests. They should also use cutworm barriers made of cardboard or newspaper around the base of the plants to prevent the pests from feeding on the stems. Applying insecticides can also be helpful in reducing the population of cutworms.
Slugs
Slugs are mollusks that feed on the leaves of Rheum rhabarbarum L. To control slugs, farmers can use beer traps or slug bait to lure and kill the pests. They can also use copper-based fungicides that repel the pests.
