Having a garden means balancing planting and harvesting. You'll want to make sure you are planting your onion sets at the right time, and harvesting them at the perfect time, so your onions have a good growing period and are out of the ground before winter flies. Understanding when onions should be growing is an important part of getting a good harvest.
Know When To Plant
Know when to plant your onion sets. Onion sets, no matter what variety of onion, are very hardy plants. They do best in cold plantings, so you'll want to plant them in the early fall as fall onion sets, or in the early spring as spring onion sets.
The variation in planting time goes along with how much time they need to grow, and you'll need to count back from there. Onion sets need about 100 days to grow, and they should be pulled before there is a hard freeze, or before it is full summer. Therefore, you need to understand your own weather. What date is the date of the first real hard freeze, usually, in your area? One hundred days before that, you should plant your onion sets.
If you are doing a spring planting, it is a little more tricky. You'll want to have about 100 days before full summer, but you'll need to wait for the ground to thaw. So, if 100 days before hot summer comes before the ground is thawed and there is a chance of a hard freeze, you'll have to wait until the ground is soft and it is not going to freeze anymore.
Know When to Harvest
Understand when to harvest to have the best onion set crop possible. Give your onion sets at least 100 days to grow. Only pull them early if there is a danger of a hard freeze, meaning that the temperature gets below freezing for more than six hours for more than two days. Pull them well before that, or they will be lost.
Harvest your onions when the stems fall. Try not to pull them when the stems are standing straight up, as they are not ready quite yet.