Yellow onion sets are a great choice for gardeners who want green onions or scallions just weeks after planting and storage onions next summer. Onions sets are extremely quick, producing mild-tasting green onions in 2-4 weeks. Harvest some for fresh eating this fall and let the rest of the sets overwinter and mature next summer. The mature bulbs are flattened with crisp, yellow-white flesh and papery skin. They're a good choice for storage and for flavoring in cooked recipes. Onion sets grow best when planted in full sun in rich, well-drained, sandy, loamy soil. After harvesting bulbs, cut the stem about 1 in. above the bulb and store bulbs in a cool, dark, dry place in shallow, open containers.