But a lot of folks encounter this problem. Rhubarb is a cool season perennial that emerges from the same crown each year. It grows best where summers are cool and winters cold enough to freeze the soil at least 6 inches deep. Growth begins when soil temperatures rise above 45 degrees Fahrenheit and the edible petioles are produced mostly at temperatures below 80 degrees Fahrenheit. Rhubarb produced in high summer temperatures has poor quality.
Hot weather encourages the elongation of a seed stalk.
The stalk is formed during the winter months and elongates sometimes , in some plants , during hot temperatures. Cool summers and high plant densities tend to retard floral development. If you notice a seed stalk on your plants, prune it out as far down near the crown as you can and don't worry about it. Go along happily harvesting the rhubarb and remember to trim off and discard the leaves. The leaf blades are filled with oxalic acid and anthroquinone and are poisonous.