You can follow the guidelines above as to how many weeks to harvest—through end of summer, before the first frost, is usually fine. Schedule just a few weeks of harvest, then give the plant time to recover, especially for winter. For each plant, harvest only about one third of the stalks. Plants should be mature (at least 3 years old) before starting to fully harvest. Stalks should be firm, not soft. Rhubarb usually can tolerate temperatures in the low 30s, even upper 20s (degrees F), but can suffer damage below that. One has to be careful about rhubarb, because if the leaves suffer cold damage, the oxalic acid from the leaves may filter into the stalks, making them toxic as well. Signs of cold damage are blackened, shriveled, limp leaves and limp, mushy stalks. If you see any damage to either leaf or stalk, discard both leaf and stalk.
You can follow the guidelines above as to how many weeks to harvest—through end of summer, before the first frost, is usually fine. Schedule just a few weeks of harvest, then give the plant time to recover, especially for winter. For each plant, harvest only about one third of the stalks. Plants should be mature (at least 3 years old) before starting to fully harvest. Stalks should be firm, not soft. Rhubarb usually can tolerate temperatures in the low 30s, even upper 20s (degrees F), but can suffer damage below that. One has to be careful about rhubarb, because if the leaves suffer cold damage, the oxalic acid from the leaves may filter into the stalks, making them toxic as well. Signs of cold damage are blackened, shriveled, limp leaves and limp, mushy stalks. If you see any damage to either leaf or stalk, discard both leaf and stalk.