When to Plant Yam/Oca (New Zealand Yam) in Brisbane — Subtropical Guide
Oca (also called New Zealand yam, uqa) is a South American tuber crop that produces colourful, waxy-skinned tubers in shades of red, orange, yellow, and white. It is a short-day tuberiser, meaning tuber formation only begins when day length drops below 12 hours. This makes it a unique autumn/winter crop in Australian gardens. Propagated from tubers, not seed.
How to Grow Yam/Oca (New Zealand Yam) in Subtropical Australia
When to Plant
REVERSE the season: plant February-March (late summer) for winter growing. The mild frost-free winters and short days in SEQ trigger tuber formation. Harvest July-August. This is opposite to temperate planting.
- Soil
- Free-draining soil rich in organic matter. Avoid waterlogging which causes tuber rot. Light, friable soil produces the cleanest tubers. Amend heavy soil with compost and coarse sand.
- pH Range
- 5.5-7.0
- Sunlight
- Full sun to light shade. Tolerates more shade than most root crops.
- Spacing
- 25cm apart, 45cm between rows
- Watering
- Keep well-watered during hot, dry periods. Oca is relatively drought-tolerant but consistent moisture improves yields. Reduce watering as foliage dies back in autumn/winter.
Companion plants: Garlic, Onion, Marigold
Avoid planting near: No known antagonisms, but keep away from other Oxalis species to prevent confusion with weeds
Subtropical Growing Tips for Yam/Oca (New Zealand Yam)
Recommended Varieties
- Red oca
- Yellow oca
- Any available varieties
Key Challenges
- Summer heat and humidity kill the plants
- Must grow as a winter crop
- Limited availability of planting material
Pro Tips
- In Brisbane/SEQ, treat oca as a WINTER crop planted in late summer
- Frost-free subtropical winters with short days are ideal for tuber formation
- The summer is too hot, humid, and wet - plants will rot or fail
Harvesting Yam/Oca (New Zealand Yam)
When ready: Foliage has completely died back (either from frost or natural senescence). This is typically 15-20 weeks after planting in temperate zones. Do NOT harvest early - tubers only reach full size in the last 6-8 weeks as the plant channels energy from dying foliage into tuber growth.
How to harvest: Use a garden fork inserted 20-30cm from the plant base. Lift the entire clump gently. Tubers are attached to the plant base by thin stolons. Collect all tubers carefully as they break off easily. Save some of the best tubers for replanting next season.
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