The blade or green leaves of the plant contain oxalic acid crystals which can cause serious problems when eaten. Crystals can cause the tongue and throat to swell, preventing breathing. Therefore, the leaves should be removed before using.
Rhubarb can be eaten after being hit by a frost or freeze PROVIDED the plant/stalks haven't wilted. If the stems appear soft and mushy, do not eat.
Rhubarb plants will occasionally send up flowers and seed stalks in the middle of the plants. The flowers and seed stalks can occur due to winter's chilling conditions. Stalks can also occur due to natural maturity of the plants.
Flower and seed stalks reduce the vigor of the plant. Energy is funneled into the stalks instead of new growth. Therefore, flower and seed stalks should be cut out as soon as they start forming. However, the plant may still continue to produce the flower stalks. Keep cutting.
Plants do NOT become poisonous after flowering starts. Leaf stalks can still be cut and used.
For more growing information, refer to Horticulture Fact Sheet VC-40-85.
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