Holly's Homestead — Bulb & Allium
Onion
Allium cepa · Onion family
DIFFICULTY Easy–moderate
TYPE Biennial, grown as annual from seed or seedlings
MATURITY 100–175 days
TYPE Biennial, grown as annual from seed or seedlings
MATURITY 100–175 days
Sun
Full sun
Water
Regular, taper before harvest
Soil pH
6.0–7.0
Spacing
10cm × 30cm
Depth
1cm
01Day-length matters
Onions form bulbs in response to day length — short-day varieties for warmer zones, long-day for cooler ones. Getting this wrong means small or no bulbs.
02Planting
Method
Sow seed or plant seedlings shallowly; choose a variety suited to your day length.
Soil
Loose, well-drained, weed-free.
Timing
Sow or plant in autumn to late winter depending on zone and variety.
Planting timing varies significantly by Australian climate zone. Set your zone above (or use the Find My Climate Zone tool) for guidance tailored to your own area.
03Growing care
- Keep beds weed-free — onions compete poorly with weeds.
- Water regularly, then stop 2–3 weeks before harvest.
- Feed lightly early on; avoid nitrogen once bulbing starts.
- Bend tops over gently once bulbing is well underway.
04Problems
- Onion thrips — silvery leaf streaking; blast off with water, encourage predators.
- White rot — soil-borne; rotate beds for years if it appears.
- Bolting — cold snap after planting; plant at the right time for your zone.
- Splitting bulbs — inconsistent watering.
05Harvest & storage
Signs
Tops yellow and fall over, necks soften.
Method
Lift with a fork once most tops have fallen.
Curing
Cure 2–3 weeks in a warm, airy, shaded spot until necks are papery.
Storage
Cool, dark, ventilated. Keeps 4–8 months.
Preserving
See Root Cellaring (curing and storing alliums) for ways to keep a harvest surplus.
Recipes
Try our Caramelised Onion — a way to use a glut.
06Companions & rotation
Plant nearby
CarrotBeetrootBrassicasLettuceAvoid nearby
BeansPeasRotation note
Avoid replanting alliums in the same bed for 3–4 years.
