Harvest onions for storage when the neck of the plant dries down, the
tops have fallen over, and the roots are dry and have stopped growing
from the stem plate. At that time the outer scales of the bulb are
drying out and do not cling tightly (outer scales of yellow-skinned
varieties change to a darker color).
Pull the onions by hand and lay in a windrow to cure with the tops
placed over the bulbs to prevent sun-scald. Onions may also be cured in
an open shed. Remove onions with thick neck (seeders) before storage and
discard all diseased bulbs.
After curing, place onions in open-slatted crates or burlap bags for
further field curing or drying. Then place in storage. You may use
either common storage or refrigerated storage.
Low temperatures in storage reduce shrinkage due to moisture loss and
stop disease development. Keep the humidity as low as possible. Good
management of ventilation is important. Ventilate storage early in the
morning.
Onions held in cold storage should be placed there immediately after
curing. A temperature of 32° F is ideal and will keep onions dormant and
relatively free of rot. If sprouts grow it indicates too high a
temperature, poor curing, or immature bulbs. If you have root growth the
humidity is too high. The humidity should be 65 to 70 percent.
Do not store onions with produce that is likely to absorb the odor.
Onions stand slight freezing, but do not handle or move them until they
thaw. You can store onions in a dry, well ventilated attic or unheated
room. Maintain as near 32° F as you can and keep as dry as possible. You
can hang open-mesh bags, about half full, from overhead hooks or nails.
Slatted half full crates of onions may be stacked on cross bars.