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Bunching Onions
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Bunching
onions are hardy perennials that are grown as annuals or overwintered for
early spring harvests. True bunching onions or scallions, Allium fistulosum, do not form bulbs
and remain straight and slender, many common onion varieties may be grown as
bunching onions, but will eventually bulb up.
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Soil and
Nutrient Requirements
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Onions
prefer soils rich in organic matter that are well-drained. Optimal pH is
6.2-6.8. They cannot tolerate acid soils, especially in early stages. 80
lbs/A nitrogen is recommended. Sidedress 4-5 weeks after planting. High
levels of sulfur in the soil will increase pungency. Best results come from
selecting a bed with the least weed pressure possible.
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Position
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Full sun.
Onions are very sensitive to day length and shade will dramatically slow
growth.
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Seeding Depth
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Planting
depth: 1/4-1/2",
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Seeding Rate
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Seeding
rate: ~50 seeds/ft, in 2-3” wide bands;
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Plant Spacing
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Thin if
desired to 2”
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Row Spacing
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Row
spacing: 12-18".
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When to Sow
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Direct
sow seeds as soon as soil can be worked. Seeds are slow to germinate
and grow, it is important to keep them well weeded so that the weeds do not
take over.
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Other Considerations
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Hill
stalks to promote elongation and blanching.
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Frost Tolerant
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Yes
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Drought Tolerant
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No
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Heat Tolerant
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Yes
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Seed Specs
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180-215M
seeds/lb (200M avg.). M=1,000
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Seed Coating /
Pelleting Info
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Some of
the varieties we carry receive an organic film coating applied to the seed,
which make the seed easier to see during planting.
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Harvest
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Harvest
when desired.
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Storage
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Store
washed shafts at near freezing temperatures.
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Pest Info
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- Onion Thrips thrive in hot
dry weather and can be discouraged by heavy rain or overhead irrigation.
Lacewing larvae, pirate bugs and predatory thrips are natural predators.
- Onion Maggots overwinter in
the soil. They feed on the roots of young seedlings, causing wilting and
sometimes seedling death. Crop rotation and beneficial nematodes can be
helpful.
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Disease Info
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- Botrytis leaf blight
(Botrytis squamosa) develops as small lesions surrounded by a
silvery-white “halo” that grow and eventually extend through the wall of
the leaf. Infection by the more common Botrytis cinerea (gray mold
fungus) is distinguished by smaller lesions that do not have a “halo”
and do not penetrate the leaf. Die-back begins at the leaf tip and can
result in premature death of the leaf prior to bulb maturity. The fungus
persists as sclerotia in the soil and on crop residues. Protectant
fungicides are applied in advance when cool, wet conditions are
expected.
- Downy Mildew (Peronospora
destructor) thrives in extended periods of cool, humid weather. Plant in
a well drained area, avoid overhead irrigation, orient rows with
prevailing winds and rotate crops.
- Purple blotch (Alternaria
porri and Alternaria alternata) appears as elongated purple lesions that
turn silvery over time. Control measures are similar to those for
botrytis blight and downy mildew. Yellow cooking onions are not as
susceptible to purple blotch as are Spanish onions. Best prevention
methods are to practice good sanitation -- never pile cull onions near
onion fields -- and crop rotation with non-host plants.
- Damping off
(Pythium/Rhizoctonia) – Avoid excessive moisture.
- White Rot (Sclerotium
Cepivorum) – Destroy infected plants and rotate crops.
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Seed Saving
Instructions
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Insect pollinated. Bunching onions are biennials or
perennials and generally will not make seed their first year. Over-winter
outside in most climates. Some staking may be necessary to hold up the top
heavy seed stalks. Harvest seed heads when 1/2 of the pods are open and
showing black seeds. Allow to dry and seeds will be easily shaken out. Use
1/8" screen to help with cleaning. Onion seeds will remain viable for
1-3 years.
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