Rheum are hardy perennials that are often used for cookery; they are large plants that can reach from 90 cm to 2.5 m in size.
Rheum has large toothed leaves and carry small white flowers atop edible stalks.
Some common names for Rheum are Rhubarb and Sorrel Rhubarb. If you are planning to grow Rhubarb for use in cooking then it is best to grow from rootstock as these will provide better flavour than seed grown rhubarb.
The Rhubarb stalks can be harvested from the second year of growth onwards and should not be harvested later than July.
Common Names: Rhubarb, False rhubarb, Sorrel rhubarb.
Life Cycle: Hardy perennial.
Height: 36 to 96 inches (90—240 cm).
Native: Europe, Asia.
Growing Region: Zones 5 to 9.
Flower Details: Green-white, rose, red. Small.
Foliage: Herbaceous. Triangular. Large. Toothed. Grown for their tart tasting stalks, and for ornamental purposes.
Sow/Growing Outside: Do not grow from seed if growing for culinary purposes. Seeds: 1/4 inch (6 mm). About one month before the last frost. Roots: Include buds. 1 to 2 inches (3 to 6 cm).
Sow/Growing Inside: Germination time: three to six weeks. Temperature: 63 to 65°F (17—18°C). Ten weeks in advance. Transplant outdoors when there is still a chance of a light frost or towards the end of autumn. As there is a large variation in size space at 12 inches (30 cm) to 60 inches (150 cm) apart depending on size. Ornamental varieties are usually grown singly.
Requirements and care: Full sunlight or light shade. Deep soil. Rich and moist soil. Mulch to maintain moisture. Provide a complete spring feed, and a weak feed every two weeks thereafter through the growing season. Regular watering during dry periods. Water during prolonged dry spells. Regular watering during periods of growth. Cut back flower inflorescences to the ground once blooming has completed in the first year. Remove inflorescences as they appear in subsequent years. Do not harvest stalks in the first year. Do not harvest later than mid-summer (late July in the Northern hemisphere). Propagate: by dividing by dividing in the spring.
Closely Related Species: Knotweed.
Miscellaneous: Rhubarb has laxative properties. Extracts of Rheum officinale are used to create the arthritis medication rheum. Although Rhubarb is a vegetable, with the leaf petiole/stalk being eaten, it is classified as a fruit in the USA. Takes from two to to five years to reach full height.
How to Grow Rhubarb
It is best to grow Rhubarb from root stock if you plan to use them for culinary puproses; these should be planted bout 3 to 5 cm deep.
If growing Rhubarb and other Rheum members as decorative plants then they can be grown from seed. Plant the seeds about 6 mm deep about a month before the last frost of spring is expected. Rhubarb can be very big plants so grow them from 40 cm (small varieties) to 1.5 m (larger Rheum members).
Rhubarb can grow in either sunny or partially shaded parts of the garden and prefers a rich and moist soil; it is important that the soil that Rheum species grow in is very deep.
If starting Rhubarb off indoors then do so about 2 months in advance (plan to plant out in late autumn, or before the last frost of spring). It should take from three to six weeks to germinate at 15 to 18 degrees Celsius.
Caring for Rhubarb and Other Rheum genus Members
To grow Rhubarb and other Rheum species successfully takes a little effort. They should be fertilized every two weeks with a weak fertilizer solution. Apply a mulch to protect them from heat, and water frequently to keep the soil moist. If you require more Rhubarb plants then they can be propagated by division in the spring.