Growing Onions, Without Tears

Many are the gardeners who have planted onions in the vegetable garden only to be left with wonderful green foliage and nothing else. Others wait the whole growing season anticipating their Bermudas or Vidalias, only to pull them out for drying and find only the smallest of pearls instead of large sliceables or eatables. But how can this be when New York is one of the most productive onion places in the world?The answer is twofold. First you must pick the right varieties for Long Island (Vidalia and Bermuda are not) and second, you must have the right soil. Unwitting errors in both of these departments lead to comments like, “I’ve tried for three years and they just won’t grow in my garden.” The truth being more like, “I’ve tried for three years and I won’t let them grow in my garden.”

For those who are successful with backyard onions, you will find that they are easy to grow, subject to few diseases, are ignored by most insects and they are easy to store for the winter. In fact, once you learn a few growing tricks these tasty vegetables need little more than planting, thinning and occasional feeding. Ma Nature takes care of all the rest.

Unlike most of our vegetables, which are annuals, onions are biennials. During their first growing season, onions store food for themselves in enlarged, modified stems so they can produce flowers and seeds in their second year. For this reason, the most successful onion growers buy onion sets or tiny bulbs that are six months to a year old and plant them instead of planting from seed, thus cutting the growing time by as much as half.

Onions, garlic, shallots and leeks are all in the same family and they all grow best in rich, loose soil. Sandy loam and peat soils are ideal, while the texture and drainage of heavier clay soils must be improved with liberal additions of compost, well-rotted manure, peat, leaf mold or other organic soil conditioners.

In Georgia, famous for its red clay, there are adequate amounts of organic matter and sand, especially in Vidalia County. On eastern Long Island it’s probably best to enrich the soil with additional organic matter, but don’t go too far, as an overly organic soil will retain too much moisture and may result in rot. Choose a spot that gets full sun and test for a soil pH of between 5.8 and 6.5. Remember also that onions are heavy feeders, so you’ll want to work in a complete fertilizer like 5-10-5 before planting and during the growing season. Good drainage controls most, but not all, onion diseases. Now is the time to plant, so you’ll need your sets, but there’s still opportunity for seeding if you have the time.

Growing from seed is the most economical way to grow onions, especially if you are going to do a large planting, but as onions are long season growers the seeds should be started from late February to early March. While growing from seed is an option, most gardeners grow onions from sets or small bulbs that are field-grown transplants sold in garden centers and by mail.

Onions need cool weather during early development to allow good growth of their secondary roots. Later, they need hot weather and the proper amount of daylight to assure the formation of plump bulbs. There are long-day and short-day varieties and it is imperative to grow the right variety or all you end up with are scallions. Varieties adapted to grow in the South, where summer days are shorter, need 12 hours of daylight to bulb, while northern varieties need 15 hours of daylight. We must grow long-day types, and for this reason it should be obvious why a Georgia Vidalia will result in tiny bulbs here, while a Walla Walla from Washington will do just fine.

Regardless of the size or maturity of the onion plant, it will start to bulb when the correct day length and temperature are reached; planting short-day varieties here in the North will therefore result in small bulbs, which are not always undesirable if you are trying to raise “pearl”-type bulbs or pickling-type onions.

To grow onions from seeds you need to begin seeding six to 10 weeks before the last heavy frost, so for us this means a first seeding around the first of February through the first week in March. Use a sterile, peat-based planting soil. Sow the seed thinly and cover with about a quarter inch of soil or vermiculite. Keep the soil moist and maintain a temperature of 60 to 65 degrees. The seeds should sprout in 10 days to two weeks, when they should be moved to a sunny windowsill or put under plant lights that are on for 12 to 15 hours a day. Thin the seedlings, if necessary, to prevent overcrowding in the flat.

In mid to late April, after the danger of a hard frost, plant the seedlings (or sets) in the garden. They should be about half the thickness of a pencil, and it’s best to do the initial planting out on a cloudy day or late in the afternoon. Space them three inches apart in rows one to two feet apart, but if you want scallions the spacing can be as little as an inch apart. These can be thinned as necessary, leaving a plant every four inches to grow to maturity.

“Sets” are small onion bulbs grown the previous year (or over the winter in greenhouses) specifically for garden starters. This is the most popular way to shorten the growing season (but not the day length), since mature onion bulbs grown from sets can be harvested a month or more earlier than those grown from seed. Sets are usually from a half to an inch in diameter, with the smaller ones being the longest to mature, while the largest may bolt to seed and produce inferior bulbs.

Sets should be planted out in early April, by making furrows about an inch deep. Press the sets into the soil, two to three inches apart in rows a foot to a foot and a half apart. Just press the bulbs into the soil up to their tops ... if planted too deep they will take longer to develop.

The third method is to buy seedlings for transplanting. This saves as much as seven weeks compared to seeding your own. Plants are usually bought in garden centers or through the mail in bunches of 75 plants, with one bunch planting a row of 18 feet. You’ll also find seedlings in cell packs. Each cell can contain about a half dozen seedlings that can be “teased” apart and planted. Plant the seedlings in prepared soil when they are received, spacing four to six inches apart in rows two feet apart. For each plant, punch a hole in the soil using your finger or a pencil, about two inches deep; carefully place one seedling in the hole, and firm around it. Keep the soil moist, not wet, until the seedlings are established.

In the case of smaller sets or seedlings, I found that some birds are very fond of simply pulling the plants out and leaving them. A row cover such as Reemay placed over the plants for a couple of weeks until they are well rooted should solve this problem.

Next week: what varieties to look for, general care after planting and harvesting, plus a look at leeks and shallots. Keep growing.