Variety Spotlight – Organic Onions!

Welcome to our new Variety Spotlight!

Each month we’ll be highlighting a particular vegetable – including our recommended varieties, planting and cultural tips, common pests and diseases, and harvest and storage tips. We’re excited to share this more detailed information with you, and welcome your comments and suggestions for future issues!

This month we’ll be discussing Organic Onions.


Our Recommended Varieties:


Calibra F1 

• A Spanish cross with a sweet and mild flavor that sweetens in storage
• Long term storage ability

 

Rossa di Milano
• Specialty onion with a sweet flavor
• Good production and storage ability
• A standout for open-pollinated onions.

 

Siskiyou Sweet Walla Walla
• Increased uniformity and disease resistance.
• Light brown skin with white flesh that is very mild and sweet.


Red Wing F1
• The ultimate sandwich onion!
• Uniform, large, round globes average 3-4”.
• Very hard bulbs are an excellent indication of its excellent storage ability.

Cortland

• Quickly becoming a standard yellow keeper for organic growers everywhere.
• We’ve been very impressed with Cortland under many conditions.

Red Baron
• Dual purpose onion for medium sized bulb onions or purple skinned bunching onions.
• Deep red outer skin and beautiful inner rings of royal purple with good color throughout.

For more Organic Onion varieties, please visit the Onion section of our website.


Planting and Cultural Tips

Onions are cool season biennials that prefer full sun, in soils rich in organic matter that are well-drained. Onions started from seed store better than sets, but mature later.

Selecting the best variety for your area:
Bulbing onions are dependant on day length for bulb production:

  • Short Day: Best for planting in the south, where hours of sunlight per day averages 10- 12 hours. (Note: you can grow short day onions in northern latitudes but they will start to bulb as soon as day length reaches 12 hours and you’ll get smaller onions.)
  • Intermediate Day: These onions start to bulb when day length reaches 12 to 14 hours. These varieties will not do well in the far south, but will do well in the rest of the country. (High Mowing carries the following “Intermediate Day” organic onion seeds: Siskiyou, Rossa di Milano, and Gladstone.)
  • Long Day: In northern latitudes (north of 35 º), with long summer days, plant “long day” onions, which begin to bulb when the days reach 14 to 16 hours in length. (High Mowing carries the following “Long Day” organic onion seeds: Calibra, Cortland, Mustang, Rossa di Milano, Redwing, Red Baron and Ambition)

Starting Onions from Seed

Start onions for transplanting 10 to 12 weeks before the last frost date in your area.

  • Sow seeds thickly in flats or 1” cells.
  • When plants emerge, thin to approx 1/8” apart.
  • When seedlings reach 5” tall, trim tops to 1” to increase girth.
  • When seedlings are pencil-thick, harden-off by exposing them to outdoor conditions while maintaining regular watering and fertility for one week before planting.
  • Transplant 4-6” apart and 1-2” deep.

Once outdoors, keep onions well watered. Watering is critical as the bulbs start to swell. Onions compete poorly with weeds, cultivate regularly to control weed pressure.

In warm regions, onions are often planted in the fall for a spring harvest of sweet onions.  In northern parts of the country, onions are planted in the spring for fall harvest of storage.


Harvest and Storage Tips

  • Curing onions in our greenhouse.

    Sweet and red onions are ready to harvest from the time bulbs begin to form throughout the summer as desired, for fresh, immediate use.

  • Storage onions can be harvested when tops dry up and flop over.
  • Dig bulbs from the ground and cure for 3-5 days in the field (if you expect fair weather) or bring into a barn or greenhouse and cure for two weeks at 75-80°F and 80% relative humidity. Too much sun exposure can cause onions to turn green.
  • Cool slowly, and store at steady temperatures. Rapid cooling followed by a sudden warm period might break dormancy and cause onions to sprout.

  • When onion bulbs have developed a papery skin and at least 1/2 of the tops have fallen over, gently push over any remaining upright tops.
  • Take care to not break stalks as this can provide an entry point for fungal or bacterial diseases.
  • Onions will start to sprout at temperatures over 40°F.
  • Inspect for damaged or soft spots on onions before storage – pull those onions out and do not store with the rest as they can affect the other onions.
  • Optimal storage is near freezing temperatures and  65-70% relative humidity.

Disease and Pests ID

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.

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. 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.

Famer Paul Betz – His thoughts on organic onions:
“Most everyone loves onions. They are a big crop for me, and I spend a fair amount of time and energy producing plants for sale and for the farm. My favorite yellow storage varieties are Cortland F1, Mustang F1, Prince F1 and Copra F1, in this order. Only Cortland F1 and Mustang F1 are available as organic seed. This past year I also grew organic Red Wing F1 and had good success. It was a bit longer to mature, but had really strong tops and could be used as a bunching onion too when bulbs were in mid-growth. For sweet onions I choose Alisa Craig and Walla Walla.”

Read more about Farmer Paul’s advice on growing large quantities of organic onions!

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