Looking at those tiny, flaky onion seeds, you’d be forgiven for wondering how they’ll ever become juicy, golden slices in your stir-fry. The truth is: onions are a slow burn.
You’ll wait up to 28 weeks (6–7 months) for harvest, but they really don’t ask for much in return—just water, time, and a little patienc
Our Trials: Seedling Trays vs. Direct Sowing
Attempt 1: Greenhouse Seedling Success
- We sowed onion seeds in trays in early spring and left them in the greenhouse.
- Nearly every single seed germinated.
- Once the seedlings had grown strong enough (about 10–15 cm tall), we transplanted them into the garden in November.
- Yes, it was painstaking moving each one, but every seedling transplanted produced a harvestable onion.
- Verdict: Slow and fiddly, but highly effective.
Attempt 2: Direct Sowing in the Garden
- Followed seed packet instructions and sowed directly into a prepared garden bed.
- The result? Only five seeds germinated.
- We’re still not sure if it was the soil, timing, or birds helping themselves, but the hit rate was dismal.
- Verdict: Not recommended unless you have perfect conditions and time to spare.
We chose Yates ‘Pukekohe Longkeeper’ and they did us well. While prone to snail attack, we had none worth writing home about. We did sow them next to the carrots (apparently their compatibility rating is good, fending off bugs). Grow in full sun, and water well.
If you are also growing spring onions in your garden, you will wonder if you mixed the seeds up! Both the seeds and the onion growth (for a certain period) seems identical. But wait, water and be patient – you will be amazed just how easy it is to grow.
You will see healthy bulbs protruding healthily from the ground. They will seem to virtually ‘sit’ on the soil and the root system is shallow and only a very small part of the onion is actually underground.
How to Grow Onions From Seed (Step-by-Step)
Sow indoors (in trays)
- Sow in late winter to early spring.
- Fill trays with fine seed-raising mix.
- Sow seeds shallowly (around 0.5–1 cm deep), spaced apart.
- Keep moist but not soggy.
- Germination takes 7–14 days in warm conditions.
- Thin seedlings to prevent overcrowding.
Transplant outdoors
- When seedlings are about 10–15 cm tall and the soil is warming (around November in NZ).
- The hollow tubular stems of your onion seedlings will be fragile, so handle with care. Lift from the seedling tray, prod the soil with a pencil approx 1cm deep and gently lower in the seedling, taking care not to damage the root system. Gently pack the soil around the roots so there are no air pockets in the soil.
- Plant around 10–15 cm apart in rows spaced 25 cm apart.
When to harvest
Onions are ready when the tops start to yellow and flop over. This is perfect, don’t be tempted to harvest them just yet. Once wilted, leave them in situ for a few weeks before harvesting.
Pick a sunny day then pull the onions out – roots and all. Dust off the dirt, and leave them in the sun or under cover outdoors for a couple of days – stems in tact.
Once the outer skins are papery, trim the tops and store in a cool, dry place or string them up. Properly cured onions can last for months.
