A garden blog I follow by a farmer in southwest Ohio posted just last week that she has already started seeds of yellow and red onions.
If this sounds too early, it is for northeast Ohio gardeners who live one zone colder than our neighbors to the south, but not by much. Onions, especially those we want to grow into large, juicy bulbs, need time to grow from seeds to "sets," which is why we buy them in early spring and put them in the ground even before the end of frosty nights.
I'm telling you this now because it is not too early to start thinking about the onion varieties we want to start from seed for our 2010 vegetable gardens.
Sure, we can stop in the local garden centers, and we should, to pick over the healthiest of the marble-sized red, yellow and white onion sets, but if we start just a few seeds of our own, which we also can buy at the garden centers, there is more to chose. Seeds aren't expensive and the packages likely contain much more than we can use in one or even two seasons.
Seeds stored in a cool, dry place in an airtight container from year to year can be viable for up to three to five years, although the germination rate decreases each year. If you miss gardening in winter, give it a try.
There are basically three types of onions, short day, long day, and day neutral, and they mean exactly that.
Short day onions begin to form bulbs when the days are 10 to 12 hours long. They are mild and have softer flesh, and they mature earlier, which is a good thing because they don't store as well as the sturdier long-day varieties. Some examples of short-day onions are the flat-shaped sweet onions, such as Vidalia, Walla Walla or Sweet Spanish. Short day onions are usually grown in the southern states and trademarked onions with specific titles, Vidalia and Walla Walla, in particular, can only be named as such provided they are grown and harvested within a set radius of where they originated in Georgia (Vidalia) and Walla Walla (Washington state).
Those onions are said to get their sweetness from the low-sulphur content of the soil in the areas where they grow. But there are plenty of other varieties of sweet onions available; they just can't call themselves by those copyrighted names.
Long-day onions are ideal for our part of the country. Those varieties start to form bulbs when the daylight hour expands to 14 to16 hours. These onions mature later, are sturdier, have thicker flesh and are more pungent. It is the sulphur content that causes the pungent flavor and that causes our eyes to tear up when we cut and chop them. (Think sulphuric acid and tear gas).
Day neutral onions don't really care about day-length. They mature according to their own plan and are easy to grow just about anywhere. Like sweet onions, they often have softer flesh and don't store as well.
Some years, I just don't get around to ordering and starting my own onion seeds, but those years when I take the time, I am always rewarded with fantastic varieties.
Italian onions, such as Bianca di Maggio is a long day onion that matures in about 110 days. It is a flat Italian onion, both sweet and mild, and somewhat small in size. A new variety available this year is Bronze D'Amposta, a larger sweet onion that is somewhat mid-way between long and short day varieties. It is a red onion and is said to be a good storage variety.
To start your onion seeds, begin with a moist, sterile seed starting mix. I prefer a soilless mix over regular potting soil as I have better success with avoiding damping off disease of new seedlings. Damping-off is a fungal disease that lives in the soil and can make an otherwise healthy plant suddenly wilt and fall over at the soil line.
Plant seeds about a quarter of an inch deep. Onions have very shallow roots, making it important to keep the soil moist. Cover the seed containers with plastic wrap or you can purchase seed starting kits with plastic domes to help keep the moisture on the surface from evaporating.
When you see the seedlings emerge, don't pull them out to thin them. Onions should be one to a cell in your seed starting container, or one to a pot, but you will need to plant three to four seeds in each one to ensure germination. When they do come up and are about two to three inches tall, use your scissors to trim all but the healthiest plant. Those trimmings can go into your salad for an early harvest treat.
Give the seedlings plenty of light. If they are growing in a south-facing window, turn them often to keep them growing straight, but the ideal conditions are beneath fluorescent grow lights. Instead of paying big prices for expensive grow light bulbs, you can put them under one cool white and one regular in a fluorescent fixture to simulate the effects of the sun. When the seedlings are small, keep the light no more than two inches above the tops of the plants. This will ensure sturdy stems and will avoid thin, leggy stems that are weak and apt to fall over.
In April, when spring starts to emerge, take your plants outdoors for a few hours each day to acclimate them to the conditions where they will soon be living. As soon as the garden soil can be worked in spring, you can place your onions directly into the garden.
Onions are heavy feeders, and a good fish emulsion fertilizer will keep them happy.
Onions are edible at any stage of their growth, so you don't have to wait until they mature to enjoy them. The more mature they are, of course, the longer they will store for winter eating, but you can enjoy them immediately while still young and tender too.