TIME TO PLANT YOUR ONIONS NOW? It depends. In growing onions the first question you must answer is “How are you going to use these onions?” Onions can be used (1) as green table onions, (2) as sweet onions for use on hamburgers and in salads as soon as they are harvested, and (3) as dry or storage onions which are usually used in cooking.

          Last week I wrote about planting onion seeds and onion sets. Now for defining short day, intermediate day, and long day in choosing onions and then about onion plants.


          In the literature and on signs in the Garden Center by the onions for sale, you will see mentioned these three groups of onions:

          Short Day varieties require fewer daylight hours to start bulb formation and to reach maturity. Therefore they are best suited for southern areas of our country. (Because the sun in summer is farther north, the southern areas have less sunlight.)

          INTERMEDIATE DAY and LONG DAY varieties require more daylight hours to start bulb formation and to mature. They will grow best in the mid and northern areas of our country because of the longer daylight during spring and summer.”(4)


          “Onion plants may be purchased by name variety.  Sweeter and milder onions do not have a long storage life. The stronger the taste of your large onion, the better it will keep and it will not bruise so easily.”

          “After purchasing onion plants, plant them as soon as possible, since they are live plants.  The onion will live approximately three weeks off the bulb and will shoot new roots after planting.  Onion plants should be planted approximately 1 inch deep with 4 inch spacing if you wish to harvest the onions during the growing season. Pull every other one as a table onion, leaving space for growth of larger remaining onions. Plants may be set out 4 to 6 weeks prior to the average spring freeze. Onion plants are hardy and can withstand temperatures of 20 degrees F.” (1)


          “The nature of the onion is to grow tops in cool weather and form bulbs in warm weather. Those varieties grown in the north require 14 to 16 hours of daylight. The reason we plant some of our varieties from plants rather than from sets is because the bulb will not get large enough unless it is already half grown and thus will mature into a big onion by the time we get to late summer and cooler weather of fall.  Good sized onion plants planted early will make a larger bulb than the normal onion set. Onion plants are the best way to grow the biggest, sweetest onions because you get a head start on the growing season. Onions are heavy feeders. One should work manure and fertilizer into the soil before planting. A pound of manure to each square foot of ground and 4 to 5 pounds of 5-10-5 fertilizer per 100 square feet will do the job.  A constant supply of moisture is essential.  It is especially important during the bulb enlargement.  Both plants and sets make excellent green onions fresh from the garden.” (2)


1. “Onions, Potatoes” and Sweet Potatoes: Planting, Growing, and Harvesting”.  Free brochure from Earl May Seed and Nursery, Shenandoah, Iowa 51503. (

2. “Onions” Free handout from Campbells Nursery and Garden Center, Lincoln, NE.  (

3. “Onions” pm1889 Revised June 2009 Prepared by Cindy Hanes, Eldon Everhart, and Richard Jauron, Extension horticulturists: Diane Nelson, extension communication specialist, and Jane Lenahan, extension graphic designer. Iowa State University: University Extension, Ames, Iowa (

4. Brown’s Omaha Plant Farms, Inc., Omaha, TX 75571, 2013 catalog.

 (Free catalog available at

Copyright 2016