GROWING GUIDE - ONIONS

Looking to grow beautiful, healthy onions in your garden? This guide covers growing from seed or sets, watering, feeding, and how to cure and store onions for long-lasting results.

QUICK FACTS

• Sun: Full sun
• Soil: Light, well-drained soil enriched with organic matter
• Spacing (bulbing onions): About 5–6 in. apart
• Harvest: On dry days; cure before storing
• Suitable for Canadian growing conditions
• Follow package instructions for best results
• Contact T&T Seeds for personalized growing advice

ONIONS PLANTING & CARE

Onions are well-suited to the Canadian climate and can be grown from seed or from sets. Depending on the variety, you can harvest onions as green onions, bunching onions, or full-size storage bulbs.

PLANTING INSTRUCTIONS

From seed:

• Start indoors mid to late March for larger bulbing onions.
• Sow into cell packs or flats and keep seedlings trimmed to about 4 in. tall to reduce tangling and encourage sturdy growth.
• Transplant outdoors once the soil is workable and temperatures have moderated.
• Space plants about 5–6 in. apart in rows about 18 in. apart.
• Direct seeding in spring works well for green onions/bunching onions.

From sets:

• Plant as soon as the soil is workable in early spring.
• Press sets into the soil so the tip is just at or slightly above the soil surface.
• Space 2–3 in. apart for green onions, or 5–6 in. apart for larger bulbs.
• If planted close together, thin as they grow to allow bulbs to size up.

CARE TIPS

Soil & watering: Onions have shallow roots and need steady moisture. Water deeply and regularly—uneven watering can lead to thick necks and smaller bulbs. Sandy soils warm early and mature sooner; peat-based soils can also perform well if drainage is good.

Stop watering before harvest: Reduce and then stop watering about 2–3 weeks before harvest to help bulbs finish and skins dry down.

Hilling: As bulbs enlarge, you can lightly pull soil around the base to reduce sunscald and help suppress weeds. Avoid burying bulbs too deeply.

FERTILIZING

Because onions root shallowly, nutrients should be available near the surface. Mix compost into the bed before planting. Feed lightly during early growth, then reduce fertilizing once bulbs begin to swell to encourage proper curing and storage quality.

If you fertilize during the seedling stage, follow label directions and avoid overfeeding—excess nitrogen late in the season can lead to thick necks and poor storage.

HARVESTING & STORAGE

• Onions are ready when tops fall over naturally and begin to dry.
• Harvest on a dry day to reduce rot risk.
• Undercut or loosen bulbs and allow them to dry (cure) in a warm, airy place out of direct rain.

STORAGE CONDITIONS

• Store fully cured onions in a cool, dry area with good airflow.
• Approximate target: ~4°C with 65–70% humidity.
• Higher temperatures can encourage sprouting; poor airflow can cause rot.

READY TO START GROWING?

Browse our selection of high-quality onion seeds and sets and get everything you need to start your garden today!

Shop now at T&T Seeds for the best selection of plants, seeds, and gardening supplies.

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