Onions and leeks are versatile crops where nearly every part of the plant is edible. They are easy to store and come in many varieties. In Canada, most onions are “long-day” varieties that create the best bulbs when daylight exceeds 14 hours. For fall plantings, look for “day-neutral” varieties.
Planting
- Starting Indoors: These have a slow growth cycle, so start seeds indoors as early as late January.
- Bulbing Onions/Leeks: Place 30–40 seeds in a 4″ pot, cover with vermiculite, and keep moist for 2–3 weeks.
- Green Onions: Plant 10 seeds per cell in 1″ trays.
- The “Haircut”: If indoor leaves start to flop over, trim them to 2″ above the soil to encourage new and stronger shoots. See the photo on the left, above.
- Transplanting Outdoors: Move to the garden around May 1st.
- Location: Choose full sun for maximum size and rich, well-draining soil.
- Preparation: Mix 1” of compost into the soil.
- Technique: Gently tease seedlings apart. Plant them individually so that the first 1/2 cm of green foliage is buried. Space individual onions 4–6″ apart.
- Green Onions: Plant entire cell plugs 12″ apart without separating the seedlings.
- Companion Warning: Avoid planting onions and leeks next to legumes, as they can stunt each other’s growth.
Maintenance
- Initial Care: Water lightly but regularly to keep delicate roots from drying out. The transplanted seedlings may initially suffer if the soil is dry but you should see new growth emerging within 2-3 weeks.
- Feeding: These are heavy feeders. Side-dress during the season with fertilizers containing nitrogen, phosphorus, and sulfur (which adds flavor).
Pests and Diseases
- Common Pests: Onions do not have many pests but the onion maggot may occasionally fid your garden.
- Prevention: Plant onions near carrots, which deter the onion fly from laying eggs.
Harvesting and Storage
- Timing:
- Green Onions: Ready 30–40 days after transplant.
- Bulbing Onions: Ready in ~90 days after transplant, once the tops flop over. See middle photo above.
- Leeks: Can take up to 120 days.
- Preservation:
- Freezing: Chop and flash-freeze green onions and leeks on a baking sheet.
- Curing: For bulb onions, brush off dirt and let them sit in a dry, sunny spot for 2+ weeks until the outer skins are dry. Store in a dark place.
💡 Tips for Toronto Gardeners 💡
In urban environments, squirrels are notorious for digging up freshly planted seedlings. Surrounding other seedlings with onions (which deter some rodents) may reduce the impacts of squirrels in the garden.
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