When to plant spring onionin Sydney.

Growing spring onion in Sydney: the specifics

Sydney sits in a warm-temperate zone with mild winters, hot summers, and year-round growing potential. Frosts are rare in coastal suburbs but can occur inland west of the Blue Mountains. The mild climate means Sydney gardeners can grow almost anything, summers are ideal for tomatoes, capsicum, and cucumbers, while winters deliver excellent brassicas, leafy greens, and root vegetables. For spring onion, the productive window in Sydney is year-round; best feb-may, aug-nov. 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 Sydney 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 Sydney

Good companions for spring onion include Carrot, Lettuce, Tomato, Beetroot. In Sydney’s 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.

Sydney-specific tips

• Sydney's wet summers (November-February) bring fungal diseases, ensure beds have excellent drainage and space plants for airflow around tomatoes and zucchini.
• Coastal Sydney rarely frosts, so you can grow silverbeet, kale, and Asian greens year-round without frost protection.
• The summer humidity makes basil bolt quickly, pinch flowers regularly and grow heat-tolerant varieties like Italian Large Leaf.

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.