Onions

Onions….Plant them in the spring or plant them in the fall!

Onions are a favorite in many households. Used in many recipes and dishes you can understand why. There are numerous varieties of onions—such as red, white and yellow—that grow to many sizes and can be used for different purposes.

If you are new to onion planting, it’s important that you understand the different ways onions can be planted and when planting should begin. Due to their biennial (or two-year-long) growing process, onions can be a bit tricky to figure out when first starting out.

The onion growing process

The first thing to note about planting onions is that they are biennial. In the first season, onions will grow from a seed to a plant and then a dormant bulb. After a period of cold temperatures, onion bulbs will grow and flower in the second season.

Onions are cool-season crops that prefer colder temperatures. Most often, onions will be planted in early spring and harvested in late fall.

You can plant onions either from seeds, sets, or transplants. When shopping for onions, you would be faced with three choices: onion seeds, sets or transplants. Each of these options is different in terms of the life cycle of onions and will produce differing results.

Onion seeds are, of course, seeds that have not begun to grow. Seeds should be planted as early as possible in the spring during cooler weather and will follow the traditional two-year life cycle from seed to bulb, then to flower the following season.

Onion sets are different—these are small bulbs harvested prematurely from the first year of an onion’s life cycle and stored through winter. Sets are easy to find and plant, but typically yield smaller onions and are more often used to produce green onions than larger bulb onions. Because sets are in the second year of the onion’s life cycle, they are more likely to bolt, or grow a flower from the center of the bulb.

Onion transplants, on the other hand, are onion seedlings started in the current growing season. Planting onion transplants in your garden at home will yield larger bulbs than you would receive from sets. Transplants are especially helpful to plant when outside temperatures are unpredictable, and are far less likely to bolt than sets.

Long-day onions, Short-day onions, and Day-neutral onions

Confused on what variety to plant in Colorado? Don’t be. You see all of them will grow and bulb in Colorado. Long-day onions need about 14-15 hours of daylight to bulb. Short-day onions need 10 hours of daylight. Day-neutral onions will form a bulb regardless of daylight hours and will produce well in almost any region. As soon as day length hits the ten hour mark, a short-day onion starts forming a bulb.

Most popular varieties of long-day are “walla walla”, “yellow and white Spanish.” These varieties require 14 hours of sunlight in order to form bulbs and are grown in the Denver and colder climates.

Most popular short-day varieties are “Georgia sweet”, “sweet red”, “Texas super sweet”, “Vidalia yellow granex” , “white granex”, and “white Bermuda. These will set bulb when the days reach 10 hours of sunlight.

Most popular day-neutral onions are “walla walla sweet”, “white sweet spanish”, and “yellow sweet spanish”. These will set bulb at any daylight hours and would work well ifyou have a slight shady area to plant.

Onion seed should be planted as soon as the soil can be worked depending on the spring weather. For Denver mid to late March is best. Earlier if seeded in side and put out the end of March. Onions can be planted into late April into May. Hard freezes can damage young seedlings.

Fall planted onion sets are planted in September or October. I plant mine in November. These sets are immature baby onions. They don’t grow much over the winter, but I get a head start in the spring. You can start harvesting by June or harvest the little green onions around Easter time. Having a crop in June is a good way to have a small crop so when I start to pickle I have some in the yard I can use.

Onion bulb formation begins when a certain day length is reached. Short-day onion varieties begin to form bulbs when they receive 10 to 12 hours of daylight, intermediate-day onions need 12 to 14 hours of daylight, and long-day varieties require 14 or more hours of daylight.

When finding a spot in your yard to plant onions find a spot that gets at least 10 hours of daylight or you will end up with all tops and no bottoms. It is also important to use a good fertilizer with a good balance 1-1-1, 2-2-2, 10-10-10 of nitrogen, phosphate and potassium in Colorado. Our soils generally have enough phosphate and potassium but are short in nitrogen. Some people feel a 1-2-1 or 5-10-5 is better suited. The onion needs a lot of fertilizer in the beginning of the season and not so much late.

Harvesting Onions

You can harvest onions at any time. There is no perfect size, just pull when they are big enough to suit you. For a full sized bulb, let onions grow and mature. They are ready to harvest when the bulbs are big and the tops begin to turn yellow and fall over. Pull them up shake off the soil, and lay them out to cure with the tops still attached. You can harvest onions at any time the bulb reaches a useable size, but for storage, you want them fully mature.

Curing the onions is as simple as leaving them out to dry after you dig them out of the ground. After you have shook off the dirt, spread them out on a dry surface out of the sun for a couple of weeks until the necks are dry and the skin is papery. After they are cured, store the onions by cutting of the top and storing them in a net bag so air can get to them. Hang them out of the light and out of any extreme heat or cold. If there are any soft ones use them up first. Keep them separated from the others so if there is a bacteria on it it won’t spread to the others. They are still ok to eat.