Onion - Harvesting
Pull green onions anytime after the tops are 6 inches tall. Green onions become stronger in flavor with age and increasing size. They may be used for cooking when they are too strong to eat raw. Though leaves are traditionally discarded, all parts above the roots are edible.
Remove any plants that have formed flower stalks and use immediately. They do not produce good bulbs for dry storage. Harvest in late July or early August, when most of the tops have fallen over. Allow the plants to mature and the tops to fall over naturally. Breaking over the tops early interrupts growth, causing smaller bulbs that do not keep as well in storage.
Pull the mature onions in the morning and allow the bulbs to air dry in the garden until late afternoon. On especially hot, bright, sunny days, the bulb may sunburn. On days when this is likely, remove onions to a shaded location and allow them to dry thoroughly. Then, before evening dew falls, place them under dry shelter on elevated slats or screens or hang them in small bunches. Tops may be braided or tied with string before hanging. Full air circulation for 2 to 3 weeks is necessary for complete drying and curing. Keep the dry wrapper scales as intact as possible on the bulbs, as they enhance the keeping ability.
After the bulbs dry, cut the tops 1 _ to 2 inches long (at or above the narrow spot where the stem bent over), and place the bulb in dry storage with good air circulation. Do not try to store bulbs that are bruised, cut or diseased, or those with green tops or thick necks. Store under cool, dry conditions. Dry onions may keep until late winter, but check them regularly and use or discard those that begin to soften or rot.
Onions from Transplants
The earlier varieties are usually ready to harvest in July, with later varieties maturing into August. When most of the tops have fallen over, the onions may be pulled and dried (refer back to Harvesting under "Onions From Sets"). The length of storage time varies with the variety, with the sweeter varieties usually being the poorer keepers.
Above 40 degrees north latitude, root maggots may attack the roots of onion plants.