When to Plant Oca in Cairns, Tropical Guide
Also called oca, New Zealand yam.
What this month normally looks like in Tropical
In October the Tropical zone normally runs 34°C by day and 23°C overnight, with about 53 mm of rain over 5 or 6 wet days. Averages 1991 to 2026, 37 postcodes, SILO.
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This Oca guide is written for the Tropical zone, which takes in Cairns, Townsville and Darwin. Somewhere else? Your postcode picks the right one.
Not your zone? Brisbane Sydney Melbourne Canberra Alice Springs Perth
Also handy: will it frost this week? and what grows in shade.
- Days to harvest
- about 17 weeks
- Sun
- Full sun to part shade
- Water
- Low
- Spacing
- 25 cm apart
- Soil pH
- 5.5–7.0
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.
Published · By GardenBuddy.au
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How to Grow Oca in Tropical Australia
- 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.
- Salt
- Moderately sensitive. Copes with a little salt, but the harvest drops on salty bore water.
- 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.
- Good companions
- Garlic, Onion, Marigold
- Keep away from
- No known antagonisms, but keep away from other Oxalis species to prevent confusion with weeds
- Grow before it
- Fruiting crops (Tomato, Capsicum, Zucchini)
- Grow after it
- Legumes (Beans - Dwarf, Peas, Broad Beans)
Give the bed 3 turns before root crops go back in. Roots fork and go leafy in fresh manure, so they take the bed after the heavy feeders have used it.
Tropical Growing Tips for Oca
Recommended Varieties
- Not suitable for tropical climates
Key Challenges
- Too hot and humid
- Insufficient day-length variation to trigger tuberisation
- Tuber rot in wet conditions
Pro Tips
- Do not attempt oca in the tropics. The physiology is wrong for this climate
- No amount of good management will overcome the day-length and heat limitations
- Consider taro, sweet potato, or cassava as alternatives
Pests and problems for Oca in Tropical
- Common Garden Snail Watch
- Slugs Watch
- Aphids Watch
- Root Rot / Tuber Rot Plant only in well-drained soil. Raise beds if necessary. Do not overwater. Ensure tubers are not sitting in saturated soil. Watch
- Oca Virus Complex Source clean planting material from reputable suppliers. Control aphids. If yield declines over several years, obtain fresh virus-free... Watch
Harvesting Oca
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.
Storing and preserving oca
How to keep it
- Cool Storage. Store unwashed tubers in a cool (5-10C), dark, well-ventilated place. Paper bags, open trays, or boxes with newspaper between layers. Higher temperatures cause sprouting; refrigerator temperatures cause sweetening. Keeps: 2-4 months.
- Sun-Curing (for sweetness). Expose harvested tubers to sunlight for 3-7 days. This converts some of the oxalic acid and increases sugar content, making tubers sweeter and less tangy. Turn daily for even exposure. Keeps: Storage life is not extended, but eating quality is improved.
- Freezing. Wash and slice or dice. Blanch 2-3 minutes. Ice bath, drain. Freeze on trays then bag. Alternatively, roast first and freeze cooked. Keeps: 10-12 months.
- Dehydrating (Chuno-style). Traditional Andean method: freeze tubers overnight (or use freezer), thaw in sun, squeeze out liquid. Repeat 3-5 times. The result is a dry, lightweight, long-storing product. In Australia, freeze in freezer overnight, thaw in sun, press. Repeat until dry and light. Keeps: 12+ months.
- Pickling. Wash and slice thinly. Pack into sterilised jars. Cover with hot vinegar brine (vinegar, water, sugar, salt). The tangy flavour of oca works well as a pickle. Ready in 1 week. Keeps: 3-6 months refrigerated.
What members get
- Soil and weather from your nearest station
- An email when it's time to sow
- Your own garden plan, including planning from a photo
- Price history and price alerts
- Pest risk alerts for your area
- Full salt and canning detail
Common Questions About Oca
What else is oca called?
Oca is the usual Australian name. Overseas seed packets and recipes call it oca, New Zealand yam. Same plant, same growing advice.
When should I plant Oca in Cairns?
Oca needs a long, cool autumn with shortening days to form tubers, and it sulks in heat over about 28C. The lowland tropics do not suit it, though a trial on the Atherton Tablelands might give a small crop.
How do I know when Oca are ready to harvest?
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.
What are the best Oca varieties for Cairns?
Recommended varieties for the Tropical zone include: Not suitable for tropical climates.
What grows well with Oca?
Good companion plants for Oca include: Garlic, Onion, Marigold.
Are oca salt tolerant?
Only a little. Oca are moderately sensitive to salt, so the harvest drops on salty bore water. Mix salty water with rainwater, and mulch the bed.
Which zone am I in?
Type your postcode into the box near the top of the page and it tells you, and links this crop in your own zone if it differs. Or look it up on the grow zone map. This page is the Tropical zone, Cairns is its reference city.