Estimated read time: 2-3 minutes
This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.
Larry Sagers Horticultural Specialist Utah State University Extension Service Thanksgiving Point Office © All Rights Reserved
Starting Plants In The Greenhouse April 5, 12, 19 and 26 form 6:00-8:00 PM with Larry Sagers and Gretchen Campbell
What a better place to grow some of your own plants from seed or cuttings than in our Garden Path Greenhouse. This course covers fertilizers, growing mixes, seed selection and transplanting, as well as insects, disease and other environmental problems. (4 week class meeting for 2 hours each week)
Register at www.thanksgivingpoint.com or call 801 768-7443 for information.
Utah produces some of the best onions in the world. Travel north into Davis, Weber and Box Elder counties and you will see onion growers planting onions as soon as the weather allows them on their fields. Following a few ideas from them will allow you to have some excellent onions that are large and tasty.
Unfortunately, many gardeners do not have success because they choose the wrong varieties. Onions are day length sensitive. That is, the length of the day determines the size of the bulb. In the Mountain West, we use long day varieties that start bulbing when day lengths reach 14 16 hours and temperatures rise above 65 degrees Fahrenheit. Cold temperatures after early planting encourages seed stalk development.
Prior to this triggering threshold, the onions develop leaves. The secret to large onions is to plant them early in the spring to allow growth as early as possible before producing bulbs. Short day onion varieties, though often sold in Utah, will not produce good bulbs. Utah Yellow Sweet Spanish, Sweet Sandwich or Walla Walla are good varieties. For green onions, use Evergreen White Bunching or Welsh Onion. (Most sets available at garden centers.)
Onions have a very poor root system and need an even supply of water and nitrogen fertilizer to produce well. Control weeds and improve the sweetness and size of the bulbs by using a thick organic mulch to cool the soil and conserve moisture.
Plant your onions in a sunny area as early in spring as soon as soil is workable. Optimal temperatures are between 45 60F. during development, and 60 75F. during bulbing and curing.
Onions are heavy feeders so apply 2 lb. of 16 16 8 (or similar fertilizer) per 100 sq. ft. Add 2 cup of ammonium sulfate (21 0 0) per 10 ft. of row 4 to 5 weeks after planting. Repeat this application 4 or 5 weeks later. Water immediately after fertilizing.
Plant sets 1 to 2 in. apart and thin them by harvesting. Place transplants 5 to 6 in. apart giving enough room for proper bulb growth. Onions can be planted in rows or wide beds so long as spacing is maintained.
Onion seeds are small so cover them lightly (3 in. deep). When using sets, firm them into the soil, root down, so that the set is just covered with soil. Amend your soil before planting because onions grown in soil containing a high percentage of organic matter germinate and emerge better and produce larger bulbs.
