Rhubarb is a perennial plant botanically classified as a vegetable, yet its tart, thick stalks are almost exclusively used in sweet applications like pies and crumbles. It is often one of the first fresh, edible crops to appear in the spring, signaling a shift in the seasons. The availability of rhubarb spans a significant portion of the year, though the exact timing depends on the specific growing method used. Generally, the season for this ingredient begins in the late winter and extends through the early summer months.
The Standard Outdoor Growing Season
The most common form of rhubarb is the field-grown variety, a cool-season plant that thrives in temperate climates. It requires winter temperatures below 40°F to break dormancy and stimulate new growth. The outdoor growing season typically begins in the early spring, with the first stalks ready for harvest in late April or early May, depending on the regional climate. In many northern regions, the harvest season continues for approximately eight to ten weeks.
Late April through June is the peak season for field rhubarb, as the stalks (petioles) are at their most tender and flavorful. The plant is harvested by taking these thick leaf stalks as they emerge from the crown. After the end of June or early July, the stalks become woodier, and the plant focuses its energy on regeneration for the next year’s crop.
This natural outdoor cycle means that traditional field-grown rhubarb is a fleeting spring and early summer treat. Growers stop harvesting by mid-summer to ensure the plant stores enough energy in its root system to survive the winter and produce a robust harvest the following spring. The quality of the stalk is closely tied to this cycle, with the earliest growth possessing the best texture.
Understanding Forced Rhubarb
The availability of tender rhubarb in cold months is due to “forcing.” This technique involves manipulating the plant’s natural dormancy by moving established rhubarb crowns indoors into dark, heated sheds or covering them outdoors to exclude light. The forcing process can begin as early as late December or January, with the stalks ready for harvest roughly seven to eight weeks later.
Forced rhubarb is distinct from its outdoor counterpart because the lack of light prevents the plant from producing chlorophyll. This absence of photosynthesis yields a visually striking stalk that is a delicate pale pink or ruby red, unlike the deeper red and green of field-grown varieties. The process also causes the stalks to grow rapidly in search of light, resulting in a more tender texture and a milder, sweeter flavor profile.
This forced method extends the rhubarb season, providing fresh stalks for consumers between January and March, well before the outdoor crop is ready. Commercial production of forced rhubarb has a long history, particularly in areas like the “Rhubarb Triangle” in Yorkshire, England. Forced rhubarb is prized for its subtle sweetness compared to the more intensely tart flavor of traditional field-grown stalks.
Safe Harvesting and Usage
The most important safety consideration is the plant’s toxicity, which is concentrated in the large, leafy blades. Rhubarb leaves contain high levels of oxalic acid, a compound that can be poisonous and cause severe symptoms like kidney damage if ingested in large quantities. Only the stalk is suitable for consumption, and the leaves must be trimmed off and discarded before preparation.
Proper technique is important for both the quality of the stalk and the health of the perennial plant. Stalks should be harvested by firmly grasping the base and pulling with a gentle twist, rather than cutting with a knife. Pulling allows the entire stalk to separate cleanly from the crown, preventing a stub that could become an entry point for disease.
When selecting stalks, look for ones that are firm and crisp, with a vibrant color, whether deep red (field-grown) or pale pink (forced). To maintain freshness, rhubarb should be stored similarly to celery: wrapped tightly in a plastic bag or damp cloth and kept in the refrigerator. This method helps the stalks retain their high water content and crisp texture for up to three weeks.