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  • Writer's pictureStronger Roots

Growing Onions

Updated: May 10, 2022


— Onions contain organic sulfur, thiosulfinates, and quercetin which all aid in cardiovascular health

— High in Vitamin C (immune health and antioxidant ), And Vitamin B

— Good source of potassium

— Red onions are rich in anthocyanins, which are plant pigments that (may) protect against heart disease, certain cancers and diabetes

— Onions are a rich source of prebiotics (digestive health) improve bacterial balance in your gut and benefit your immune system

— Antibacterial properties


— Plant seeds, sets (immature bulbs grown from previous season), or transplants (seedlings started the same season)

— Sow seeds 1/4” deep ; Plant transplants 1-2” deep; plant Sets pointed end up and covered in 1” of soil

❗️WIDEST choice of cultivars when selecting seed; start seeds Late winter!!

❗️Sets LEAST likely to develop disease issues

— Plant I’m well-drained, Loam Soil

— Start seeds 8-15 weeks (indoors) before planning to transplant in the garden

❗️Too Keep onion transplants from becoming too tall and floppy, clip the tops back every week

— Plant sets and transplants outdoors as soon as soil temperatures reach and sustain 35° / direct sow seeds when the soil temps reach 40°

— Plant set and transplants 4-6” apart in rows 1-2’ apart

— plant multiplier onion sets 6 to 8 inches apart each way

— Prepare soil at least 8 inches deep


— Thin 1 1/2” apart (Indoors) and 1” apart (outdoor) ; Thin to 1inch when they are 4” tall

— Half a day to Full Sun

— Temps between 60° and 70°

— Ph 6.0-7.0

— Adding potassium and phosphorus amendments will encourage early maturation

— Remove weeds using hoe (or similar tool) to SLICE weeds near surface being careful not to disturb onion roots

— Keep soil constantly moist ❗️dry soil can cause splitting of onions; If tops being to start to yellow, cut back on watering


— Long-Day - Onions start forming bulbs when they receive 14-16 hours of sunlight each day


— Short-Day 10-12 hours of light to initiate bulb formation


— Intermediate-Day start growing bulbs when daylength reaches 14-16 hours



— Plant bulb onion cultivars close together and harvest early as green onions or SCALLIONS

— — Harvest green onions when tops are 6 inches tall

— Multiplier onions can you add up to 12 bulbs for each one planted

— When tops of bulbs start to yellow the bulbs are maturing; When 2/3 have fallen over

— Carefully pull or dig onions up from the ground with the tops intact. Gently shake the soil from around the bulbs

— When the weather is dry, the plants can be pulled from the soil and laid right in the garden for a day or two (For Curing)

❗️ As the onions are curing, their necks will gradually wither and the papery skins will tighten around the bulbs

❗️ Any bulbs that have bolted, or formed flower stalks, should be pulled and used right away


— Choose Yellow cultivars - recommended for their long storage life

— Cool dry place; Humidity range of 65-70%

— Pungent onions that will be stored for the winter need to be cured for two to four weeks. A good storage onion stored properly will retain its eating quality for 10 to 12 months


— Apply parasitic nematodes( a week before planting) if you’ve had issues with cutworms or onion maggots in the past

— Floating row covers for pest problems such as onion maggots

— Purple blotch : spray sulfur to reduce the spread of this disease

— Sunscald: protect onion tops from sitting in the sun

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