Onion Pukekohe Long Keeper

Starting Seeds in Trays 

Steps: 

1.Seed Trays: Use modular trays or small pots with a fine seed raising mix (not garden soil). 

2. Sowing: Plant 2–3 seeds per cell, 6mm deep. Lightly cover with mix. 

3. Germination: Keep moist and warm (18–25°C). Seeds sprout in 7–14 days. Use a heat mat if needed. 

4. Light: Place under grow lights or in a sunny window (12+ hours daily). Rotate trays to prevent leggy seedlings. 

5. Thinning: Once seedlings are 5cm tall, snip weaker ones, leaving 1 strong plant per cell. 

6. Hardening Off: 1–2 weeks before transplanting, gradually expose seedlings to outdoor conditions (start with 1 hour daily). 

7. Transplanting: When seedlings have 3–4 leaves (8–10 weeks old), plant 10–15cm apart in prepared beds. 

Pros: 

• Extends growing season in cooler zones. 
• Protects seedlings from pests/weather early on. 

Cons: 

• Requires more effort and equipment (lights, trays). 
• Risk of transplant shock if not hardened properly. 

Direct Sowing 

Steps: 

1. Soil Prep: Loosen soil to 30cm depth. Mix in compost or aged manure. Remove weeds. 

2. Sowing: 

• Create shallow furrows 1cm deep. 
• Sow seeds 2–3cm apart, then cover lightly with soil. 
• Water gently to avoid dislodging seeds. 

3. Spacing: Thin seedlings to 10–15cm apart when 5–8cm tall (use thinnings as green onions). 

4. Mulching: Apply straw or sugar cane mulch to retain moisture and suppress weeds. 

Pros: 

• Less labour intensive. 
• Avoids transplant shock. 

Cons: 

• Slower growth in cool soil. 
• Vulnerable to pests (e.g., slugs, birds) and weather extremes. 

Key Tips for Both Methods 

 Watering: Keep soil consistently moist until seedlings establish. Reduce watering as bulbs form to prevent rot. 

 Fertilising: Apply a nitrogen rich fertilizer (e.g., fish emulsion) every 2–3 weeks until bulbs swell, then switch to low nitrogen feed. 

 Pest Control: 

• Cover seedlings with insect mesh to deter onion flies. 
• Sprinkle diatomaceous earth around plants for grub prevention. 

 Thinning: Crucial for bulb development—crowded onions stay small. 

 Common Mistakes 

1. Overcrowding: Leads to competition for nutrients and stunted bulbs. 

2. Poor Drainage: Onions rot in waterlogged soil—ensure raised beds in wet climates. 

3. Late Transplanting: Seedlings older than 10 weeks struggle to adapt. 

Hacks 

 Tray Starter Hack:

• Trim seedling tops to 10cm tall if they become leggy. This strengthens stems. 

 Direct Sow Hack:

• Mix radish seeds with onion seeds—radishes mark rows and break soil crust for onion sprouts. 

Harvest 

 When:

• Tops yellow and fall over for full size onion. Lift bulbs gently. 
• Before bulb starts to swell for spring onions

 Curing:

• Dry in a shaded, ventilated area for 2–3 weeks. Store in mesh bags in cool (0–4°C), dark conditions. 

 Companion Planting Guide 

Plant With: 

• Carrots: Deter each other’s pests (onion/carrot flies). 
• Brassicas (cabbage, kale): Repel cabbage worms. 
• Tomatoes/Capsicums: Onions deter aphids and beetles. 
• Chamomile: Enhances onion flavour. 
• Marigolds: Suppress nematodes and beetles. 

Avoid: 

• Legumes (peas, beans): Compete for nutrients. 
• Asparagus: Inhibits growth. 
• Other alliums (garlic, leeks): Attract shared pests like onion maggots. 

 Seed Saving Guide 

1. Select Bulbs: Save seeds from large, disease free onions. 

2. Overwinter: Replant best bulbs in spring; onions flower in their second year. 

3. Isolate Varieties: Prevent crosspollination by spacing varieties 1 – 2km apart or bagging flower heads. 

4. Harvest Seeds: Let flower heads dry on plants. Shake seeds into a container and remove chaff. 

5. Storage: Keep in airtight containers in a cool, dry place. Seeds remain viable 1–2 years. 

Troubleshooting 

 Pests: Use neem oil for thrips or onion maggots. Interplant marigolds for nematode control. 

 Diseases: Rotate crops yearly to prevent fungal issues (e.g., downy mildew). Avoid overwatering. 

 Weeds: Mulch with straw or plant quick growing greens (lettuce, rocket) as living mulch.