EXTENSION CONNECTIONS: Growing sweet bulb onions

Now is the time to prepare for next springs sweet onion harvest. 

There are numerous varieties of onions that will produce large bulbs in north Florida. They are usually broken into two groups, the granex (hybrids) and grano (open-pollinated) types. 

The yellow granex varieties are those produced as Vidalia onions in Georgia. Varieties that have produced well in Florida include Caramelo, Nirvana, Sweet Caroline, Honey Comb and Sugar Belle. All of these are yellow varieties.

Late transplanting, such as in February, may result in smaller bulbs unless crop is managed intensively. Desirable transplant size is about a quarter inch in diameter, or about as thick as a pencil. Plants should be set 1 inch to 2 inches deep and soil firmed around them. 

The bed should be moist and kept moist until new growth is observed. In-row spacing should be no closer than 4 inches.

How much phosphorous (P2O5) and potassium (K2O) amounts to apply should be based on soil test results. A general recommendation for total amounts of nitrogen, phosphorous and potassium would be about 130-160-160 pounds an acre. 

Greater amounts of nitrogen and potassium may be needed depending upon rainfall. All the phosphorous, and about 50 pounds each of nitrogen and potassium, should be applied before planting. 

The additional nitrogen and potassium should be spaced out over the crop season. Excessive early nitrogen fertilization may result in lush growth which may be damaged by cold weather.

Several diseases such as downy mildew, blast, or tip blight, or purple blotch may occur. Diseases must be identified for proper control recommendations. 

Consult your local extension agent for approved fungicides and help in disease identification. There are very few insect pest problems in onions. At times, mole crickets, worms, thrips or onion maggots may be a problem.

Home gardeners will harvest the sweet onions in early May. When onions reach maturity, their necks become soft and their tops fall over.

Stop watering the plants when the first tops fall over. When about 30 percent to 40 percent of tops have fallen over, you may gather the crop. 

Pull the onions and let them air dry for three to four days out of the sun. Clip the tops and roots off and store in a cool dark place. 

The mild, short-day onions produced in Florida cannot be stored for long periods of time, usually less than two months. 

If you need more information, or have any questions, call your local county extension office at 689-5850.

Gerald Edmondson is the director of the Okaloosa County Extension office in Crestview, located at 5479 Old Bethel Rd.