White Onion Sets, 1 Lb Pack 1 Lb White Onion Sets, Approx. 70-80 Bulbs Onion sets are small "baby" onions (bulbs) that are used to grow green onions or dry onions. They are planted in early spring and in 4 to 5 weeks you will have green onions. If left to fully mature, you will have dry onions in late July or early August. Height: 12 - 18 inches. Spacing: 2 - 4 inches apart. Depth: Plant sets 1 - 2 inches deep and 2 - 4 inches apart.