Onions are "love 'em or leave 'em" vegetables. For some, there is no substitute for these aromatic bulbs, while others are afraid to grow them for fear of contaminating their soil. Onions are all members of the allium family. This family comprises some 600 species, including garlic, chives, scallions, leeks and flowering alliums. Onions have long been used for food, feeding the builders of the pyramids and Greek and Roman troops as they conquered the world. Gen. Ulysses S. Grant wrote the War Department a dispatch saying, "I will not move my armies without onions."
Growing large tasty onions takes more than just luck. Variety selection is absolutely critical because onions are either short- or long-day varieties. Long-day onions are best for our area, as they form larger bulbs. Long-day onions require 14-16 hours of daylight and are planted early in the spring, as soon as the soil can be worked. These varieties form bulbs when the days are the longest in the summer. Onions often fail to produce sizeable bulbs because sets of short-day varieties are planted.Shawn Olsen, Utah State University Extension agent in Davis County, works with many commercial onion growers and offers these tips for successful onion production:
"Variety selection is absolutely critical. Walla-Walla, Spartan Sleeper, Utah Sweet Spanish, Fiesta, Vega, Armada and Mamba (a nice, red onion) are excellent choices. Some of these are commercial varieties and may not be readily available at local garden centers."
Olsen also suggests starting the onions from seed. The most common complaint of gardeners is that their onions never grow large. Using seeds instead of sets will help solve this problem. Generally sets have already been through one growing period and often form seed heads instead of bulbs. Additionally, many of the sets are grown in the Southern United States and are short-day varieties not well-adapted to this area. Earlier crops are grown by using transplants instead of sets.
Good bulbs need good leaf growth before the bulbs start to form. Olsen recommends a complete fertilizer at planting time and side dressing with nitrogen fertilizer every four to five weeks. Onions are very shallow rooted and should never be stressed for water. Sprinkling works very well and also helps control thrips, a major onion pest.
Thrips turn the leaves a silvery color and interfere with food manufacture, so the bulbs don't get as large. The tiny, slender insects move quickly and often go undetected by the untrained eye. Maggots can also be a problem. These small worms feed on the bulbs, making them unusable. Diazinon granules in the furrow at planting time is the preferred treatment.
The most serious disease is pink root. The roots turn pink and rot, and yields are severely reduced. Rotation is the best way to control this problem. Cold temperatures immediately after planting will cause onions to bolt or go to seed. This is most serious when sets are used. Onions are not competitive, so keep them weed-free for the best crop.
Harvesting onions is a simple process. A common myth to hasten maturity is to break or stomp the tops of onions. This is not necessary and can even be detrimental. To hasten maturity, reduce the water. If onions are for storage, wait until the tops die down, dig them and allow them to dry in a warm, shady place until the skins turn papery. Store in mesh bags in dry, well-ventilated locations. Storage temperatures can get to 32 degrees Fahrenheit without adversely affecting onion quality.
Plant overwintering onions Aug. 1 and leave them in place. They are ready for harvest in June of the following year. Green onions, chives and scallions are also popular. They are immature bulbing onions or bunching onions and are planted throughout the season and used as needed. They are cold hardy and grow well from sets, seeds and transplants. Plant successive crops throughout the year for continuous harvests.
Whether you love 'em or leave 'em, onions are a popular, widely grown vegetable. Choose the right varieties and provide the right growing conditions to assure a supply of flavorful, attractive onions for your hamburgers, county fair or other desires.
- THE FOLLOWING WORKSHOPS are at the Salt Lake County Government Center, 2001 S. State St., South Building, Room S1007-8. Classes are held from 2-4 p.m. OR 7-9 p.m. Instructors: Larry Sagers and Jerry Goodspeed, USU Extension horticulturists.
- March 18 - Growing vegetables workshop
- April 8 - Small berries workshop
- April 21 - Turf Workshop
Larry A. Sagers is a horticulturist with the Utah State University Extension Service.