image by Net_efekt: Flickr.com
Rhubarb is a perennial plant in the Polygonaceae family. Rhubarb plants have large stalks that produce leaves and flowers. The stalk is the portion of the plant that is eaten, and the flower and leaves are discarded. Although rhubarb is used mostly for pies and jellies, it is considered a vegetable.
Harvest rhubarb when the stalks are between 10 and 15 inches long. The stalk is the celery-like, curved reddish portion of the plant. If all of the stalks have not grown to this size, do not remove the smaller stalks.
Remove only a few stalks of rhubarb the first year it has been planted. Although new rhubarb plants can withstand a very light harvest, pulling every stalk off the new plant will weaken it and possibly keep it from growing in future years.
Don't depend on the color of the stalk. Different varieties of rhubarb produce bright red stalks (the Ruby and Valentine cultivars) while others (the Victoria and Linneaus cultivars) are usually only red at the bottom of the stalk when the rhubarb is ready for harvest. Just because the rhubarb is not entirely red does not mean it should not be harvested.
Cut the stalks you wish to harvest with a sharp knife. Cut as close to the base of the plant as possible, without injuring any small plants that may still be growing. Trim off any excess leaves after washing the stalks.
Remove flowers as they grow. Even if you are not harvesting your rhubarb this year, pinch off the small flowers that grow on top of the stalks. These flowers take nutrition from the stalk and can prevent it from growing to its full size.