Great Plains Gardening

By Edith Koeller

February 27, 2004

Last I heard the soil temperature was 36 degrees. Could it be planting time? If you are thinking of onion seed, perhaps so. According to Burrell’s seed catalog, growers near Rocky Ford plant from Feb. 20 to April l, when the temperature is at least 35 degrees. Many gardeners prefer to buy the plants from reliable garden suppliers. Whatever is your preference; let us consider onions this week.

There are many onion varieties available: red, white, yellow, mild, pungent, deep or flat globed, long or short storing, available as plants, seeds, or sets.

Onion sets usually are grown for fresh green onions since normally they do not grow as large as the transplants and seed onions.

Planting seed onions requires more labor intensive care, but a wider selection of varieties is available than in both sets or transplants. A ¼ ounce of seed will sow a 100 ft. row.

Onions are considered as long-day, short-day; and day neutral. Long day varieties require 12-13 hours of daylight for best development so are more suitable for the north. Short day varieties need less daylight while the day neutral varieties do well most anywhere.

Onions do best in a fertile, well-drained garden soil with abundant organic matter. Soils that are a stiff clay, light sandy, or wet, mucky will not produce a large globe. If you plant where you grew a good corn crop last year, the location for onions should work fine.

The CSU Extension office has a fact sheet, Onions and Related Species #7.614, available for interested gardeners. The following is quoted from that source. "Plant onion seed in March, if possible, but no later than May 1. Onions are affected by day length and begin to bulb when the day length reaches 12 hours and the temperature reaches 70 degrees. Once bulbing begins, top growth stops. If the tops are small when this happens, the onions will be proportionally small. The pearl onions seen in the; frozen food cases are produced in this way—by growing a short-day onion, such as Crystal Wax, under long day conditions."

"Onion sets and transplants may be planted later than seed and still produce normal size bulbs. However, planting after May 1 decreases the average bulb size, while planting before April 2 increases the percentage of seed stalks."

"Plant onion seed 1 inch deep. Thin the plants as they grow so the bulbs never touch. Thinned out plants may provide green onions. The spacing between rows need be only wide enough to permit cultivation, generally 1 to 2 feet. Because onions are shallow rooted, they require frequent irrigation."

I have found that using the space between rows for a furrow for irrigation works very well, since the growing bulbs should not stand in water.

"Among the insects that are likely to attack onions are the onion maggot and thrips. A single onion maggot will ruin a bulb. If they are expected, treat the soil with Diazinon prior to planting, according to label directions. Thrips are tiny and may escape observation. However, when the insect population builds up, the leaves will take on a silvery appearance. When this occurs, it is time to spray with Diazinon or Malathion as directed on the labels."

"Onion diseases should no present a problem unless the ground has had a history of diseased onion crops. When diseases are noticed, they should be identified. Your local CSU Extension can help identify the disease and can recommend a treatment. To avoid losses from storage diseases, be sure onions are well cured before storing."