Direct sow seeds in spring, in full sun location, and well-drained, organically rich soil after the threat of frost has passed. Sow seeds 1 in. deep, 3-4 ft. apart in rows 18-24 inches apart. Grown from seed, rhubarb plants take about 3 years to mature to first harvest. In optimal growing conditions two-year old stalks can be harvested from healthy plants. The leaves are not for consumption, only the red, tart stalks will be used. A packet of seed will produce about 20 plants.