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In the UK, ocas go in the ground early May to early August.
Ocas (Oxalis tuberosa) — Tuberous, short-day perennial grown as an annual crop.
Timing is the decision that matters most in the UK: there are 4 separate regional sowing windows, ranging from early May in Southern England to mid May in Scotland.
Core growing advice on this page is checked against named horticultural sources — see References.
Cultivariable states planting runs from after the final frost through August; taken here as roughly May to early August for southern England's frost-free window.
Midlands - detail & sources
Same after-last-frost planting window as elsewhere in the UK.
Northern England - detail & sources
Planting window opens about a week later than southern England, reflecting a later last-frost date -- RHS rates oca H2, not surviving an actual freeze, so frost timing matters more than in hardier crops.
Scotland - detail & sources
Planting window opens about two weeks later than southern England for Scotland's later last-frost date, and the shorter autumn before the first hard frost can cut into the short-day tuber-bulking period -- worth planting as early as frost risk allows.
Tuberous, short-day perennial grown as an annual crop. RHS rates it H2 (1-5C, tolerant of low temperatures but not surviving freezing). Cultivariable notes it survives to USDA zone 9a (20-25F minimum) but most of that zone runs too hot in summer for good tuber yields.
Cultivariable: plant whole tubers 2-3in deep, 18in spacing between plants, 24-48in between rows for good air circulation; plant after the final frost, through August in cool climates. RHS: separate and replant tubers in autumn or spring.
Vegetative growth
3
Cultivariable: performs best in full sun where summer highs stay below 85F with cool nights; give partial shade in hotter spells. Loose, light soil with added compost or organic fertiliser supports easy tuber harvest later.
Short-day tuber initiation
4
Cultivariable: tuber formation only begins once day length drops to 12 hours or less, starting after the autumn equinox (22-23 September) -- around six weeks of short days is needed before a reasonable harvest is possible.
Harvest
8
Cultivariable: harvest no earlier than early November, with the third week of November giving roughly 80% of potential yield; loose soil makes lifting the tubers easier and reduces damage.
When to pick: Cultivariable: harvest no earlier than early November -- tuber formation only begins after the autumn equinox once days shorten to 12 hours or less, so a third-week-of-November harvest captures roughly 80% of potential yield.
Storage
40F/4C at 90%+ humidity gives storage life over a year (Cultivariable); flavour mellows and loses acidity over 4-6 weeks if stored at room temperature instead.
Named by Cultivariable: lower stems blacken and soften.
Oca virus diseases (Papaya mosaic virus and unidentified potyviruses)
low
Named by Cultivariable in some varieties, typically mild in impact; RHS's UK conservatory-context page reports the crop as generally disease-free, a genuine difference in growing context kept honest rather than merged.
Oca decline (symptom complex: knobbly tubers, early sprouting, reduced yields, fasciation)
low
A named symptom complex from Cultivariable: knobbly tubers, early sprouting, reduced yields, and fasciation.
Bacterial soft rot (oca tubers, causal agent not yet confirmed)
moderate
Named by Cultivariable affecting tubers; no specific bacterium identified.
A well-established planting of oca (Oxalis tuberosa) -- flowering doesn't need to be encouraged or removed for a good tuber crop, unlike some root vegetables.
Oca's leaves are unmistakably clover-like, in three heart-shaped leaflets -- a useful identification feature, since oca is a distant relative of common wood sorrel and shares its leaf shape.
Cultivariable notes oca performs best where summer stays below 85F with cool nights -- conditions that also keep the foliage looking fresh like this through the growing season.
Cultivariable notes tuber formation only begins after the autumn equinox once days shorten to 12 hours or less -- a harvest like this depends on getting several weeks of that short-day period before the first hard frost.
Light: full sun in cool climates, partial shade where temperatures often exceed 80F; requires short days (12h or less) to initiate tuber formation, beginning after the autumn equinox. Soil: loose, light soil for easy harvest, tolerates poor soil, benefits from compost/organic fertiliser, pH 5.5-7.5 (optimal 5.5-7.0). Size: ~18in tall (often sprawls lower), 2-3ft spread, tubers 4-8in long, 1.5in wide. Hardiness/climate: best where summer highs stay below 85F with cool nights (low 70s F or cooler); survives to USDA zone 9a (20-25F) but most of that zone is too hot in summer; well suited to Pacific Northwest and coastal California. Planting: whole tubers 2-3in deep, 18in spacing between plants, 24-48in between rows; plant after final frost through August. Propagation: tubers, or stem/stolon cuttings rooted before tuber formation; seed has no dormancy and a short viable lifespan. Pests: voles cause significant tuber damage especially at harvest; tarnished plant bugs target flowers; wireworms cause mostly cosmetic tuber damage. Diseases: stem rot (lower stems blacken/soften), bacterial soft rot on tubers, "oca decline" symptom complex (knobbly tubers, early sprouting, reduced yields, fasciation), mild viruses including Papaya mosaic virus and unidentified potyviruses. Harvest: no earlier than early November, third week of November gives ~80% potential yield. Storage: 40F/4C at 90%+ humidity gives over a year of storage life; oca loses acidity in storage, lowest after 4-6 weeks at 70F.
Hardiness H2 (1-5C, tolerant of low temperatures but not surviving freezing). Soil: loam, sand, well-drained, acid/alkaline/neutral pH. Sun/aspect: full sun to partial shade, east/west-facing. Exposure: sheltered. Size: 0.1-0.5m height and spread, 2-5 years to maturity. Propagation: separate and replant tubers in autumn or spring. Pests: potentially vulnerable to vine weevil. Diseases: generally disease-free. Edible use: produces edible, fleshy, red or yellow tubers, grown as a food crop as well as ornamentally.
2 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.
Frequently Asked Questions
When should I sow ocas in the UK?
In Southern England, from early May. In Scotland, wait until mid May. Treat these as a guide rather than a fixed date — the governing rule is to sow only once frost risk has passed and temperatures are reliably warm enough.
When do I sow ocas?
Sow early May to early August.
What problems affect ocas?
Our data links 4 diseases and 4 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
Most of the advice on this page comes down to timing and spacing — sowing at the right moment, rotating beds, and giving plants enough airflow. The UK Garden Planner lays your plot out month by month so those decisions are already made before the season starts.
UK vegetable growing guides · Checked against RHS & Met Office guidance
Every SoilCommander guide is written and maintained by our editorial team for real UK growing conditions, and reviewed against Royal Horticultural Society growing advice and Met Office climate data before publication.
Sketch your exact plot shape, pick your UK crops, and get a spacing-accurate bed layout with companion pairings, a rotation plan and month-by-month sowing dates — every fact sourced from RHS and Garden Organic.
