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Onions

May 05, 2009 -

Soil Preparation

Onions prefer loose, well-drained soils that are high in fertility, slightly acidic, adequately irrigated and exposed to full sunlight. The looser the composition of your soil, the larger your onion bulbs will grow. Prepare your bed by turning under animal manure or plant residue based compost, making sure that this material is fully broken down before planting. Compost composed of cedar or redwood is not an acceptable substitute for high quality compost. The potential for fungus diseases like downy mildew and pink root can be greatly reduced by avoiding beds where onions, garlic and other alliums have been grown within the last two years. This time period is a basic rule of thumb but, in general, “the longer the better”. As gophers are a major pest in onion beds, use gopher traps, wire barriers and wire baskets prior to and during planting.

Planting & Growing Onion Transplants

We ship Onion Transplants in the fall as this is the optimum time to plant them in mild climates. Onion Transplants are often wilted when they arrive, but like other members of the hardy lily family, they will survive for about 2 weeks after being pulled from the soil. If you cannot plant them immediately upon receipt, either refrigerate them after soaking the roots in water or mound soil around the roots and keep them moist until planted.

Before planting, trim Onion Transplant tops to approximately 3” and roots to 1/4” - roots will begin to grow rapidly once planted. Plant Onion Transplants 1”- 2” deep (to the top of white section) and 4”-6” apart. Plant close as 3” apart if smaller onions are desired. Rows should be 18”-24” apart or 12” apart if planting for commercial production.

If planted on raised beds which are approximately 20” wide, transplants should be planted in double-rows 4” from each edge. “Scatter planting” among vegetables in inter-planted gardens is sometimes utilized to ward off a variety of pests, but onions must not be forced to face heavy competition from surrounding neighbors.

Onion Sets

Onions are easy to grow from sets. Plant 1” deep and 1-3” apart. Harvest young plants for use as scallions, thinning to 3-4” spacing. Onions should be mulched and supplied with ample phosphorus while growing. Mulch deeply (up to 8”) in cold winter areas but only lightly in milder climates. Mulching will suppress weeds, maintain soil moisture and protect bulbs from “heaving” (working their way out of the soil) during extreme temperature cycles. Weed suppression is critical for onions -you can grow weeds or onions, but not both. Regular irrigation is necessary anytime rainfall is not sufficient to provide the 1” of water per week required to keep bulbs from splitting in hot dry soil or tasting bitter at harvest. Water up until the time you harvest! Beds kept weed free and properly irrigated will require little additional care.

Harvesting & Storing

Onions are mature and ready to harvest when their tops have yellowed and begin to fall over. Finish bending the tops horizontal to the ground by hand or with a rake for those that have not completely fallen over. This bending will stop the sap from diverting energy into the leaves while the bulb matures. Harvest bulbs after the tops have turned brown. Place the tops of one row over the bulbs of another to keep them from becoming sunburned. When the outer skins have dried, complete harvesting by clipping the roots, wiping off any remaining soil and cutting the tops back to 1” above the bulb.

Onions keep best when kept separated; individual foil wrapped specimens can last up to a year under refrigeration. Pungent onion varieties, which have low water content, will keep longer than sweeter, moister types. Hanging an onion in a mesh bag, in a cool, dry, well-ventilated location and tied off to separate onions from each other, is the recommended method of preserving onion bulbs for maximum shelf life.

Organic Onion Transplant Combo Pack

The six varieties of onions and leeks are labeled like so:
Red = Red Torpedo
Light Blue = Red Crimson
Green = Walla Walla
Yellow = Stockton Yellow
Black = Solano White
Brown = Varna Leek



Robert Jarrell Says:
Oct 28th, 2012 at 1:16 pm

I just planted sets. 10/28/12 I water the dry loose soil after plannting. I added blood and bone meal and compost to soil before planting. These are raised beds with a drip system. Since it is the beginning of fall/ winter do I continue to water every week or do I wait until the spring when I have sprouts? This is my first try.

Charlotte from Peaceful Valley Says:
Jan 28th, 2013 at 12:26 am

Robert, As Sarah says here, regular watering is needed if you don’t have 1” of rain a week. Water them until maturity, when the tops will fall over http://extension.usu.edu/files/factsheets/onionsf.pdf

Maria Brophy Says:
Feb 26th, 2013 at 8:17 pm

I am ordering the yellow onion sets to plant in Southern California.  What type of soil should I buy to plant them in?  Also, is March a good time to plant them?  I am new to gardening and so I could use some guidance!

Charlotte from Peaceful Valley Says:
Mar 4th, 2013 at 1:39 pm

Maria, Onions sets can be planted as early as February, so March is fine.  They will need a soil with fine tilth and good drainage.  A well balanced fertilizer and trace minerals may be necessary as amendments, if you’re unsure of the components of the soil.  Do a soil test, either lab or home http://www.groworganic.com/fertilizers/soil-test.html They will also need a sunny location. Sets planted in March will probably be ready for harvest around September, when a new crop can be planted if desired for a June harvest the following year.

Sue Hansen Says:
Mar 16th, 2013 at 3:30 pm

I live in the mountains of Idaho, zone 4. Can I plant onion sets in the fall for late spring harvest? We get feets of snow all winter (Oct-March) and subzero temperatures part of the winter. Also, can you recommend any books or publications for High Altitude Gardening? thanks

Charlotte from Peaceful Valley Says:
Mar 27th, 2013 at 10:55 am

Sue, Zone 4 is just not prime onion growing territory.  If you put sets or transplants out with your summer garden (making sure they are good companions with their neighbors),you can probably harvest fist-sized onions in the fall.  Drying the resulting onions might be an issue, but could be done in mesh bags that are propped up on something that allows air flow all around (like a mesh propagation tray). 

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