Plant 2-3 ft. apart in rows 3-5 ft. apart. Mulch plants and regularly irrigate them during the summer. Break off any flowering stalks back to the ground so that the plant’s energy goes into producing stems. Harvesting: Rhubarb leaves are poisonous - only the stems are edible. Wait until the second year to harvest stems from plants started from seed. Mature plants can be harvested twice a week for 6-8 weeks in the spring. Harvest 1⁄3-½ of the stems, leaving at least 5 stems still growing.