Rhubarb is a great candidate for greenhouse production. By forcing rhubarb outdoors and then transferring it to a greenhouse, the plant's growing season is extended. Typically, greenhouse-grown rhubarb is ready for consumption in February and March, months before the outdoor-cultivated variety.
Hothouse rhubarb is usually a brighter red than cultivated rhubarb. Hothouse rhubarb is also more tender and tastes sweeter than cultivated rhubarb.
Rhubarb is often "forced" to develop the most tender, sweetest stalks. Forcing rhubarb involves excluding light from the young crown. In the greenhouse environment, where light is amplified, rhubarb can be forced by covering the young crowns with a container. Alternatively, the rhubarb can be planted outdoors and then moved into the greenhouse. Forcing takes approximately four weeks.
Rhubarb is grown primarily in northern locations, such as the northern United States and Canada. The hot and dry conditions found in the southern U.S. are not ideal for rhubarb production, even in winter months. Rhubarb is a cool-season, perennial crop. It requires temperatures below 40 degrees Fahrenheit to break dormancy and to stimulate growth. Rhubarb grows best in temperatures between 50 and 60 degrees Fahrenheit.
Rhubarb is grown in moderately acidic soil. For maximum yield, soil pH should be maintained at around 6.0 to 6.8. Rhubarb responds well to fertilizers. Commercially grown rhubarb receives approximately 1,500 pounds per acre of 10-10-10 fertilizer. Rhubarb prefers diffused light; therefore, ideal conditions can be met by growing the plant through the winter in a greenhouse. Rhubarb is a very hardy plant, subject to only a few diseases. Root rot is the only disease of large consequence. Root rot is caused by growing the plant in damp, poorly drained soil. In the greenhouse, where growing conditions can be controlled, it is easy to prevent an outbreak of root rot. Good circulation in the greenhouse is paramount to preventing an outbreak of fungus.
To grow a healthy plant with a solid root system, do not harvest rhubarb in the first year. When plants are kept in production for their entire lifespan, no more than half the stalks are harvested at a given time. Once planted, rhubarb plants remain productive for eight to 15 years.
Rhubarb leaves are toxic due to high concentrations of oxalic acid. Cooking the plant will reduce the concentration of oxalic acid. Oxalic acid poisioning can lead to cardiovascular and respiratory failure or even death. Children are especially sensitive to oxalic acid.