Common Name: Rhubarb
Scientific Name: Rheum species
Family: Polygonaceae (the Knotweed, Smartweed, Buckwheat family)
Common Species:
- Himalayan Rhubarb (Rheum australe)
- Sikkim Rhubarb (Rheum nobile)
- Turkey or Chinese Rhubarb (Rheum palmatum)
- Da Huang (Rheum palmatum tanguticum)
- False Rhubarb (Rheum rhaponticum)
- Common Rhubarb (Rheum rhabarbarum)
- Garden Rhubarb (Rheum x cultorum or Rheum x hybridum)
Description:
Rhubarb, along with Asparagus, is one of the more well known perennial vegetables. The large green leaves and red stalks were once a very common site in the home garden. Nowadays, there are probably more people who have heard of this vegetable than have eaten it, although the sour leaf stalks are still commonly used in pies (typically mixed with berries and lots of sugar) or in jams (also with lots of sugar). Few people in the U.S. have eaten Rhubarb as a vegetable as they do in Asia, and even fewer people have eaten the immature flower buds like cauliflower.
History:
Almost all of the nearly 60 species of Rhubarb are used for food, medicine, or both. Originally from Asia, and grown for thousands of years, Rhubarb has been distributed around the world.
Trivia:
- Most commonly found Rhubarb have red stems, but there are a number of varieties (and other Rheum species) that have green or pink stems.
- Rheum palmatum is a large plant that can reach 6-10 feet tall and reportedly has a gooseberry-flavored stalk
- Rheum australe is reported to have an apple-flavored stalk.
USING THIS PLANT
Primary Uses:
- Edible Stalks – very tart. Typically cooked, but some eat them raw. In the United States, Rhubarb is cooked like a tart fruit in pies and jams, with the addition of a lot of sweetener (sugar, honey, etc.), while in Asia, Rhubarb is eaten as a vegetable similar to celery and can be used in soups and stews. Rhubarb stalks have been candied as well.
- Edible Flower Buds – cooked; similar in texture to cauliflower, but very tart.
- NOTE: due to the high amounts of oxalic acid in this plant, Rhubarb should be eaten in moderation. So what does this mean in real life? Don’t eat Rhubarb with every meal for a week. Oxalic acid inhibits the body from absorbing calcium. Over time, this can be harmful. However, considering its tartness, excessive consumption is unlikely.
Secondary Uses:
- Pioneer Plant Species
- Groundcover – plant larger species (Rheum palmatum) at 4 feet (1.2 meters); plant other species at 2.5 feet (0.8 meters)
- Dynamic Accumulator
- Biomass – on the small scale, but the leaves are not eaten, so use them for compost
- Insecticide Plant – simmering leaves in hot water yields an insecticide solution (I can find no recipes or application instructions)
- Dye Plant – some species leaves, stalks, and roots can be used to make yellow to red dyes.
Yield: Depends on the species, variety, growing conditions, and harvesting techniques.
Harvesting: Spring – Early Summer. Cut or twist off the leafstalk. Make sure to avoid the roots and the leaves. By mid to late Summer, the oxalic acid content has climbed, and even the stalks should be avoided or at least eaten in very limited quantity. Many people, mainly commercial growers, will harvest all the stems at once. This likely puts undue stress on the plant and encourages it to go to seed. Instead, remove no more than about a third of the stalks at one time and only mature stalks; harvest the next batch of now mature stalks a few weeks later. This method will also extend the harvesting season. It is time to stop harvesting once the stalks get thin.
Storage: Eat, cook, or process right away. Fully mature stalks will keep in a cool dry place (like a refrigerator) for a few days. Stalks can be frozen as well; pre-cutting and pre-measuring will make using them easier.
DESIGNING WITH THIS PLANT
USDA Hardiness Zone:
Himalayan Rhubarb (Rheum australe): 5-8
Sikkim Rhubarb (Rheum nobile): 7-9
Turkey or Chinese Rhubarb (Rheum palmatum): 4-7
False Rhubarb (Rheum rhaponticum): 3
Common Rhubarb (Rheum rhabarbarum): 3-8
Garden Rhubarb (Rheum x cultorum or Rheum x hybridum): 1-9
AHS Heat Zone: Garden Rhubarb (Rheum x cultorum or Rheum x hybridum): 8-5
Chill Requirement: No reliable information available.
Plant Type: Herbaceous Perennial
Leaf Type: Deciduous
Forest Garden Use: Herbaceous Layer
Cultivars/Varieties: Many species and many, many varieties available.
Pollination: Self-Pollinating/Self-Fertile. Pollinated by wind.
Flowering: Summer
Life Span:
Years to Begin Bearing: Rubarb will put out stems right away, but they should not be harvested the first year. A few can be harvest the second year.
Years to Maximum Bearing: 3-4 years is when you can start harvesting in earnest
Years of Useful Life: 10-15 years if not divided. If divided, the plant will live indefinitely.
PHYSICAL CHARACTERISTICS OF THIS PLANT
Size: 3-5 feet (0.9-1.5 meters) tall and wide for R. x cultorum, other species are larger.
Roots: Fibrous and Deep (Rheum nobile has a root that can get to 7 feet (2 meters) long)
Growth Rate: Fast
GROWING CONDITIONS FOR THIS PLANT
Light: Prefers full sun
Shade: Tolerates light shade
Moisture: Medium
pH: most species prefer fairly neutral soil (6.1 – 7.0)
Special Considerations for Growing:
- Being hardy to Zone 1, Rhubarb is one of the most cold hardy perennial vegetables available.
- If you live in areas warmer than Zone 7, consider growing Rhubarb as a Winter annual or consider growing a more heat tolerant species (Rheum palmatum, Rheum nobile).
- The garden varieties are great for gardens and good soil, but consider some of the other species if you are planning on using Rhubarb as a pioneer species or planting in soil that is less than ideal.
Propagation:
Usually by division in Spring. Can be planted from seeds, but seeds do not always produce plants similar to their parents (not true to type) – seeds do not require cold stratification.
Maintenance:
- Almost none. Very resistant to pests and disease.
- Crowns should be divided while dormant (either late Autumn or early Spring) every 4-5 years.
- Consider composting the leaves and stalks that dry up at the end of the season
Concerns:
Poisonous – Leaves and roots are toxic. There is a high amount of oxalic acid in the leaves, but it is likely the presence of an unknown glycoside that is the cause of its toxicity, not the oxalic acid.
