Onion Plant FAQ'sHere are some onion plant FAQ’s that we often get asked. This information is brought to you by the Texas AgriLife Extension Office.

1.     What onion varieties should be planted to produce large, sweet bulbs?

Plant the varieties 1015Y, Granex, White Bermuda or Burgundy. These onions are considered short­ day onions. Planted at the right time for your area and given proper moisture, fertility, and weather, they should produce large, sweet bulbs.

2.  What are the characteristics of these varieties?

1015Y– One of the sweetest, mildest of all onion varieties. Introduced by the South Texas onion industry in 1985 after 1O years of research. Produces a globe-shape that can be very large, sometimes weighing over a pound and measuring over four inches in diameter. The 101SY is disease resistant and stores better than other varieties grown in North Texas.

Yellow Granex – Produces a thick, flat sweet yellow onion. This is the type of onion that is planted to grow the famous Vidalia onion. But to be legally labeled Vidalia, the onion must be grown in one of the 16 counties near Vidalia, Georgia. It is an early-maturing onion but does not store well.

White Granex – This variety has the same characteristics as the yellow Granex but with pearly-white flesh.

White Bermuda – An old variety that has been planted as a favorite of many gardeners for years. White Bermudas are also known as Crystal Wax and produce thick, flat bulbs that are extremely mild. However, they do not store well.

Burgundy – A sweet variety for those who prefer a red-skinned onion.

3.  What is the difference between a set and a transplant?

Although many gardeners use these terms interchangeably, there is a difference. An onion set is a small bulb, up to one inch in diameter. It is produced under conditions which rapidly produce a small bulb. These bulbs will produce green onions but often do not produce a large bulb. An onion transplant is a plant between 8 to 10 weeks old which has not gone through the bulbing process, and if planted at the right time will produce large bulbs. A slip is another term used to describe a transplant.

4.  What varieties of green onions grow well?

The term green onion describes an immature onion. Even the large bulb onions such as Granex can be harvested immature and used as green onions. Some gardeners who seed these varieties of onions directly in their garden selectively thin them as they grow and use the thinnings as green onions. The shallot, a multiplier-type onion with a distinct flavor, is also used as a green onion.

5.  What is a bunching onion?

Several types of onions are used as green bunching onions. Evergreen is a frequently planted variety of this type. They may be planted from seed, sets or transplants. Bunching onions are generally classed as multipliers because they propagate themselves. They are cold resistant and can be grown during winter. They will not bulb and are harvested as needed, using both the root and the tops.

6.  What is a shallot?

A shallot is a member of the multiplier-type onion family which lives for many years and is grown for its mild, garlic-flavored roots, made up of segments called cloves. The plants will grow to be about 18 inches tall and often bear white or violet flowers in early summer.

7.  What is the difference between green onions and leeks?

A leek has a much milder flavor than an onion. The term scallion describes leeks and green onions.

8.  How and when should onion transplants be planted?

Onion transplants should be placed approximately one inch deep and about four inches apart. Should you want to harvest some of the onions as green onions, you may plant as close as two inches apart. Pull every other one, prior to them beginning to bulb, leaving some for larger onions.

Transplants should be set out four to six weeks prior to the date of the last average spring freeze. However, many gardeners plant as early as January in North Texas.

9.   Is it necessary to remove the garden soil from around onion bulbs in the spring to make large bulbs?

No. Bulbing of onions is controlled by variety, temperatures, and length of day. The onion will bulb when the required conditions are met. Removing soil around the base of the plant will not increase bulbing, although it appears to because the bulbs are visible. This operation may do more damage than good, especially to white varieties of onions. Removing the soil from around white onions results in sun burning which turns the top of the bulbs green.

10.  Every year I buy onion plants to be set out in the spring in my garden. Some years they make nice size bulbs and other years they don’t. Why?

There is no simple answer to this commonly-asked question. First of all, obtain varieties which will bulb in your particular area. Always buy plants about the size of a pencil or smaller. Larger plants will not produce earlier or produce larger bulbs. Generally, a large onion plant will produce a seed stalk after planting instead of forming a large bulb. Always set the plants in your garden at the right time for your area.

11.  Should I break over the tops of my onion plants to get a larger bulb?

A: Breaking over the tops of onion plants will not increase bulb size but can prevent bulb enlargement. Onion bulbs increase in size as sugars manufactured in the top are translocated to the bulb. If the tops are broken, this process stops.

12.  What causes my bulb onions to send up flower stalks?

Most people want to grow onion bulbs, not onion flowers. The flowering of onions can be caused by several things, usually temperature fluctuation. An onion is classed as a biennial which means it usually takes two years to go from seed to seed. However, this condition is triggered by temperatures. If an onion plant is exposed to alternating cold and warm temperatures resulting in the onion plant going dormant, resuming growth, going dormant and then resuming growth again, the onion bulbs prematurely flower or bolt. Flowering can be reduced by planting the right variety at the right time. Use only transplants that are pencil-sized or smaller in diameter.

13. Should I remove the flower stalks _from my onion plants?

No. Once the onion plant has bolted or sent up a flower stalk, there is nothing you can do to eliminate this problem. The onion bulbs still will be edible but probably will be smaller. Use these onions as soon as possible because the green flower stalk which emerges through the center of the bulb will make storage almost impossible.

14.  After harvesting, what is the best way for me to store my onions?

Onions should be stored in a relatively cool, dry place. Sweet onions will not store as long as more pungent varieties.

The maximum length of storage of sweet onions will run from 2 to 3 months. Allow onions to fully mature in the garden before harvesting. Maturity is indicated by the fall of the top of the onion plant. After the tops have fallen, pull and dry the onions in the garden for several days. After drying, remove the roots and the top, leaving about 3/4 to 1 inch of the neck to seal and prevent entrance of decay.

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