The size of the onion bulb is dependent upon the number & size of the green leaves or tops at the time of bulb maturity. For each leaf there will be a ring of onion; the larger the leaf, the larger the ring will be. The onion will first form a top, then depending on the onion variety & length of day light, start to form the bulb. Onions are characterized by day length; "long-day" onion varieties will quit forming tops & begin to form bulbs when the day length reaches 14 to 16 hours, while "short-day" onions will start making bulbs much earlier in the year when there are only 10 to 12 hours of daylight. A general rule of them is that "long-day" onions do better in northern states (north of 36th parallel) while "short-day" onions do better in states south of that line.
Care Of Onion Sets
When you receive live plants, they should be planted as soon as possible. Should conditions exist that make you unable to plant these plants right away, remove the onion plants from the box & spread them out in a cool, dry area. The roots & tops may begin to dry out, but don't be alarmed... the onion is a member of the lily family & can live for approximately three weeks off the bulb. The first thing that the onion will do after planting will be to send out new roots.
Preparing the Soil
Onions are best grown on raised beds or raised rows at least 4" inches high & 24 inches wide. Onion growth & yield will be greatly enhanced by adding a fertilizer rich in phosphorous (10-20-10) 2 to 3 inches below transplants at planting time. Make a trench in the top of the bed fours inches deep, distribute one-half cup of the fertilizer per 10 linear feet of row, cover the fertilizer with two inches of soil & plant the transplants.
Planting
Set plants out approximately one inch deep with a minimum 6" spacing. On the raised bed, set 2 - 4 rows on each bed, four inches in from the side of the row. . Up north, transplants should be set out 4 to 6 weeks prior to the date of the last average spring freeze. Here in the south, transplants should be set out 4 to 6 weeks prior to the date of the 1st average freeze.
Fertilization & Growing Tips
Onions require a high source of nitrogen. A nitrogen-based fertilizer (ammonium sulfate or ammonium nitrate) should be applied at the rate of 1 cup per 20' of row. The first application should be about 3 weeks after planting & then continue with applications every 2 to 3 weeks. Once the neck starts feeling soft, do not apply any more fertilizer. This should occur approximately 4 weeks prior to harvest. Always water immediately after feeding & maintain even moisture during the growing season. The closer to harvest the more water the onion will require. For organic gardeners, a rich compost high in nitrogen should be incorporated into the soil. While cultivating be careful not to damage the onion bulb. As the onion begins to bulb, the soil around the bulb should be loosen so the onion is free to expand. Do not move dirt on top of the onion since this will prevent the onion from forming its natural bulb.
Disease & Insect Control
The 3 major diseases that will affect onions are the funguses downy mildew, blight & purple blotch. If a purplish gray fuzzy growth develops on leaves, that is downy mildew. Should the leaves turn pale-green, then yellow, blight has probably affected the plant. Purple blotch causes purple lesions on the leaves. Heavy dew/foggy weather favor their rapid spread & when prolonged rainy spells occur in either cool or warm weather, these diseases can be very destructive. The best cure is prevention... use only well-drained soil, run the rows in the same direction as prevailing wind & avoid windbreaks or other protection. Should conditions persist, a spray with a multi-purpose fungicide can be applied on a 7 to 10 day schedule.
The insect that causes the most damage is the onion thrip. They feed by chewing the surface of the leaves & then sucking the juices. They are light-brown in color & are approximately 1mm long. The most available insecticides are Malathion or liquid Sevin may be used. Do not apply any insecticide within seven days of harvest & always follow label instructions.
Flowering Is Not Good For Onions
Most folks want to grow onion bulbs NOT onion flowers!!! What causes bulb onions to send up flower stalks? Flowering of onions can be caused by several things but usually the most prevalent is temperature fluctuation. An onion is classed as a biennial which means it normally takes 2 years to go from seed to seed. Temperature is the controlling or triggering factor in this process. If an onion plant is exposed to alternating cold & warm temperatures resulting in the onion plant going dormant, resuming growth, going dormant & then resuming growth again, the onion bulbs prematurely flower or bolt. The onion is deceived into believing it has completed two growth cycles or years of growth in its biennial life cycle so it finalizes the cycle by blooming. Flowering can be controlled, to some extent, by planting the right variety at the right time, however it is mostly up to mother nature.
What can one do if flower stalks appear??? Should the flower stalks be removed from the onion plants??? It's up to you... once the onion plant has sent up a flower stalk, there is nothing you can do to eliminate this problem. Use these onions as soon as possible because the green flower stalk emerges from the center of the bulb will make storage impossible.
Harvesting & Storage
Onions are fully mature when their tops have fallen over. After pulling from the ground allow the onion to dry, clip the roots & cut the tops back to one inch. The key to preserving onions & to prevent bruising is to keep them cool, dry & separated. In the refrigerator, wrapped separately in foil, onions can be preserved for as long as a year. The best way to store onions is in a mesh bag or nylon stocking. Place an onion in the bag & tie a knot or put a plastic tie between the onions & continue until the stocking is full. Loop the stocking over a rafter or nail in a cool dry building & when an onion is desired, simply clip off the bottom onion with a pair of scissors or remove the plastic tie. Another suggestion is to spread the onions out on a screen which will allow adequate ventilation, but remember to keep them from touching each other. As a general rule, the sweeter the onion, the higher the water content & the less shelf life. A more pungent onion will store longer so eat the sweet varieties first & save the more pungent onions for storage.
Care Of Onion Sets
When you receive live plants, they should be planted as soon as possible. Should conditions exist that make you unable to plant these plants right away, remove the onion plants from the box & spread them out in a cool, dry area. The roots & tops may begin to dry out, but don't be alarmed... the onion is a member of the lily family & can live for approximately three weeks off the bulb. The first thing that the onion will do after planting will be to send out new roots.
Preparing the Soil
Onions are best grown on raised beds or raised rows at least 4" inches high & 24 inches wide. Onion growth & yield will be greatly enhanced by adding a fertilizer rich in phosphorous (10-20-10) 2 to 3 inches below transplants at planting time. Make a trench in the top of the bed fours inches deep, distribute one-half cup of the fertilizer per 10 linear feet of row, cover the fertilizer with two inches of soil & plant the transplants.
Planting
Set plants out approximately one inch deep with a minimum 6" spacing. On the raised bed, set 2 - 4 rows on each bed, four inches in from the side of the row. . Up north, transplants should be set out 4 to 6 weeks prior to the date of the last average spring freeze. Here in the south, transplants should be set out 4 to 6 weeks prior to the date of the 1st average freeze.
Fertilization & Growing Tips
Onions require a high source of nitrogen. A nitrogen-based fertilizer (ammonium sulfate or ammonium nitrate) should be applied at the rate of 1 cup per 20' of row. The first application should be about 3 weeks after planting & then continue with applications every 2 to 3 weeks. Once the neck starts feeling soft, do not apply any more fertilizer. This should occur approximately 4 weeks prior to harvest. Always water immediately after feeding & maintain even moisture during the growing season. The closer to harvest the more water the onion will require. For organic gardeners, a rich compost high in nitrogen should be incorporated into the soil. While cultivating be careful not to damage the onion bulb. As the onion begins to bulb, the soil around the bulb should be loosen so the onion is free to expand. Do not move dirt on top of the onion since this will prevent the onion from forming its natural bulb.
Disease & Insect Control
The 3 major diseases that will affect onions are the funguses downy mildew, blight & purple blotch. If a purplish gray fuzzy growth develops on leaves, that is downy mildew. Should the leaves turn pale-green, then yellow, blight has probably affected the plant. Purple blotch causes purple lesions on the leaves. Heavy dew/foggy weather favor their rapid spread & when prolonged rainy spells occur in either cool or warm weather, these diseases can be very destructive. The best cure is prevention... use only well-drained soil, run the rows in the same direction as prevailing wind & avoid windbreaks or other protection. Should conditions persist, a spray with a multi-purpose fungicide can be applied on a 7 to 10 day schedule.
The insect that causes the most damage is the onion thrip. They feed by chewing the surface of the leaves & then sucking the juices. They are light-brown in color & are approximately 1mm long. The most available insecticides are Malathion or liquid Sevin may be used. Do not apply any insecticide within seven days of harvest & always follow label instructions.
Flowering Is Not Good For Onions
Most folks want to grow onion bulbs NOT onion flowers!!! What causes bulb onions to send up flower stalks? Flowering of onions can be caused by several things but usually the most prevalent is temperature fluctuation. An onion is classed as a biennial which means it normally takes 2 years to go from seed to seed. Temperature is the controlling or triggering factor in this process. If an onion plant is exposed to alternating cold & warm temperatures resulting in the onion plant going dormant, resuming growth, going dormant & then resuming growth again, the onion bulbs prematurely flower or bolt. The onion is deceived into believing it has completed two growth cycles or years of growth in its biennial life cycle so it finalizes the cycle by blooming. Flowering can be controlled, to some extent, by planting the right variety at the right time, however it is mostly up to mother nature.
What can one do if flower stalks appear??? Should the flower stalks be removed from the onion plants??? It's up to you... once the onion plant has sent up a flower stalk, there is nothing you can do to eliminate this problem. Use these onions as soon as possible because the green flower stalk emerges from the center of the bulb will make storage impossible.
Harvesting & Storage
Onions are fully mature when their tops have fallen over. After pulling from the ground allow the onion to dry, clip the roots & cut the tops back to one inch. The key to preserving onions & to prevent bruising is to keep them cool, dry & separated. In the refrigerator, wrapped separately in foil, onions can be preserved for as long as a year. The best way to store onions is in a mesh bag or nylon stocking. Place an onion in the bag & tie a knot or put a plastic tie between the onions & continue until the stocking is full. Loop the stocking over a rafter or nail in a cool dry building & when an onion is desired, simply clip off the bottom onion with a pair of scissors or remove the plastic tie. Another suggestion is to spread the onions out on a screen which will allow adequate ventilation, but remember to keep them from touching each other. As a general rule, the sweeter the onion, the higher the water content & the less shelf life. A more pungent onion will store longer so eat the sweet varieties first & save the more pungent onions for storage.
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