When to plant spring onionin Canberra.

Growing spring onion in Canberra: the specifics

Canberra has Australia's most extreme capital city climate, bitterly cold winters with frosts from April to October, hot dry summers, and a compressed but highly productive growing season. The altitude (580m above sea level) and inland location create temperature extremes few other Australian cities experience. Canberra gardeners must plan carefully around the frost calendar, but the cold winters produce outstanding garlic, broad beans, and brassicas, while hot dry summers are ideal for tomatoes once frosts are safely past. For spring onion, the productive window in Canberra is august-april. Within that window, Spring onions are the workhorses of the raised bed garden, compact, fast, and multi-purpose. They can be grown as a long-term crop (pulling individual plants as needed) or as a short-term succession crop for continuous harvest. Sow seeds 1-2cm deep in rows 15cm apart, with 5cm spacing within rows. Alternatively, buy bundles of seedlings at the nursery and plant them directly. Spring onions tolerate close spacing well and can be grown more densely than most vegetables without competition. Succession sow every 3-4 weeks for continuous harvest. The fastest harvest comes from buying seedling bundles and planting direct; seed-sown plants take 60-80 days but provide a more cost-effective ongoing supply. To regrow spring onions after harvest, leave 3-4cm of the white base in the ground, new shoots will emerge within a week or two. Alternatively, place the cut bases in a glass of water on a windowsill and transplant the regrown sections. Spring onions are outstanding companion plants when interplanted with carrots in alternating rows, their contrasting scents confuse both carrot fly and onion fly. Plant them along the edges of raised beds as a companion border. Feed lightly with a balanced fertiliser every 3-4 weeks. Spring onions are not heavy feeders but benefit from a topdressing of compost during the season. They are relatively pest and disease resistant compared to bulb onions.

Sizing it for your household

Maintain a row of 20-30 plants at various stages; succession sow every 3-4 weeks 1 plant per harvest; regrows 2-3 times after cutting. Plant Planner does this maths automatically once you tell it your household size, it’s the part most planners get wrong because they assume every household is the same.

The 5 cm spacing (with 15 cm between rows) means a standard 1.2 m × 2.4 m raised bed in Canberra can hold 384 spring onion plants at maximum density, though in practice you’ll want to mix companions in, so plan for roughly 60-70% of that.

Companion plants for Canberra

Good companions for spring onion include Carrot, Lettuce, Tomato, Beetroot. In Canberra’s cool temperate climate, these pairings reduce pest pressure and improve pollination. Keep spring onion away from Beans, Peas, they fight for the same nutrients or attract shared pests.

Canberra-specific tips

• Canberra's last frost is typically around late September-early October, never plant frost-sensitive crops (tomatoes, beans, zucchini) outside before mid-October.
• The short frost-free window in Canberra means starting tomatoes, capsicum, and basil indoors from late August is essential to get a decent harvest before April frosts.
• Canberra's low humidity and sunny summers make it excellent for disease-free tomatoes, far less fungal disease than coastal cities.

Common problems

Thrips cause silver streaking on leaves and can spread iris yellow spot virus, control with spinosad spray or reflective mulch. Onion leaf blight causes elongated lesions with dark borders, improve airflow and avoid overhead watering. Downy mildew appears as pale patches with furry growth, remove affected material. Snails and slugs eat young plants; use iron-based bait.

Harvest

Pull individual plants when they reach pencil-width or thicker. The entire plant is edible, white bulb, green stem, and even flowers. For a continuous harvest, pull alternate plants and allow the remainder to continue growing. Wash and use immediately or store upright in a glass of water in the fridge for up to a week.