Rhubarb is a cool season crop recognized by its large green leaves and red stalks. The leaves should not be used for food, as they are poisonous. Before using rhubarb in recipes, remove all leaf tissue and use only the stalks. The stalks are similar to celery with a strong sour or tart flavor.
Although rhubarb is a vegetable, it is classified as a fruit due to its use in pies, jams, and liquors.
Types & Varieties
Rhubarb is generally available in three types: red, speckled (pink), or green. Of the red type, there are several Crimson varieties including Crimson Cherry, Crimson Red, and Crimson Wine. These varieties produce stalks of bright red.
In addition to the Crimsons, there are also Valentine, Canada Red, and Cherry Red. Cherry Red is distinguished by its deep red color and long, thick stalks. Most red varieties are more tender than others.
Speckled or pink varieties include Victoria which produces large, long, round stalks. The pink speckling is more pronounced at the bottom of the stalk while the tops are light green.
Similar to Victoria, German Wine is more vigorous with darker pink speckling. Riverside Giant is a green variety that produces long, large, green stalks.
Rhubarb prefers well-drained, fertile soil in full sun. Temperatures below 40°F in winter and below 75°F in summer are best, which is why most commercial production of rhubarb is in the Pacific Northwest, California, and Michigan (for both fresh market and processing).
Plants should be spaced several feet apart in weed-free soil to reduce pests and disease. During the first year of growth, do not add chemical fertilizer as direct contact with nitrates will kill plants.
Rhubarb requires sufficient water during the summer months. To establish plants, do not harvest during first growing season.
Stalks should be removed with a gentle twist or cut from the base of the plant. A few stalks must remain on the plant for continued production.
Rhubarb meant for processing has all leaf matter removed and is cut at both ends, while fresh market stalks are not cut at the basal end and still have about a quarter-inch of leaf material attached to the petiole.
High levels of oxalic acid—a white, crystalline substance—may be found in freeze-damaged stalks and is what makes rhubarb leaves poisonous. If the plants freeze, the oxalic acid can travel into the stalks making them poisonous as well.
Pests & Diseases
Japanese beetles feed on leaves leaving little behind but veins and are extremely destructive as both adults and larvae. Potato flea beetles eat holes in leaves and much like a flea, can jump if disturbed while feeding.
Army worms feed primarily on leaves. For approximately two and a half weeks, larvae feed on the plants before moving to the soil to pupate. After two weeks, the moths emerge.
Crown rot is noticed in the lower leaves when they turn yellow, then brown, and wilt. Damaged stalk bases are brown with a mushy texture.
Root rot is the result of poor drainage or over-watering. Highly rich organic soil will help with prevention.
Ramularia leaf spot first appears as tiny red dots on the leaves. These dots continue to grow up to a half-inch or more in diameter and change color from red to tan.
As with both crown and root rot, well-drained, fertile soil can help prevent the disease. Infected leaves should be removed promptly and plant debris destroyed after the first frost.
References: Iowa State University, Ohio State University Extension, Oregon State University, Purdue University, UC Davis Postharvest Technology Center, University of Minnesota, Virginia Cooperative Extension.
GRADES & GOOD ARRIVAL
Generally speaking, the percentage of defects shown on a timely government inspection certificate should not exceed the percentage of allowable defects, provided: (1) transportation conditions were normal; (2) the USDA or CFIA inspection was timely; and (3) the entire lot was inspected.
|U.S. Grade Standards||Days Since Shipment||% of Defects Allowed||Optimum Transit Temp. (°F)|
Canadian good arrival guidelines (unless otherwise noted) are broken down into five parts as follows: maximum percentage of defects, maximum percentage of permanent defects, maximum percentage for any single permanent defect, maximum percentage for any single condition defect, and maximum for decay. Canadian destination guidelines are 15-10-5-10-3.
References: DRC, PACA, USDA.