Oca

Quick facts

Category

roots bulbs

Difficulty

intermediate

Days to harvest

180 to 240 days

Harvest type

single harvest then replant

Spacing

30 cm between plants

Environment

Temperature

8–22°C

pH

5.5 to 7

EC (hydroponic)

1.2 to 1.8 mS/cm

Daily light

14 to 22 mol/m²/day

Climate and zones

USDA zones

7 to 10 (winter low around -18°C or warmer)

Frost tolerance

frost sensitive (dies at first frost)

Season

cool (spring and fall crops)

Viable growing environments:

• outdoor in growing season (annual)
• unheated greenhouse / hoop house

USDA zone bounds reflect outdoor year-round survival. Anywhere outside the bounded zone range, this crop still grows as an annual in the warm months (outdoor_seasonal), under cover (greenhouse), or indoors under lights.

Growing systems

Oca works in:

• soil bed

Growing media

The substrate the roots sit in. Choice depends on the system (clay pebbles don't fit NFT channels; rockwool isn't used in media beds) and the crop (oca works in the media listed below).

Bacterial surface area matters for aquaponics: clay pebbles, lava rock, and pumice double as biofilter substrate. Low-surface media (rockwool, perlite, pea gravel) work in hydroponics but need a separate biofilter in aquaponics.

Nutrient demand by stage

NPK ratios are relative weights at each growth stage; the nutrient mix calculator scales them to absolute grams or ml. EC targets shift through the plant's life: seedlings need a much lighter solution than fruiting adults.

Aquaponics suitability

Not recommended for pure aquaponics. Fish waste alone doesn't provide enough of the nutrients this crop demands (typically potassium, calcium, or boron). It can be grown in a hybrid system where the reservoir is supplemented with hydroponic-style nutrients, but expect to dose actively.

Care notes

A specialty tuber crop requiring specific conditions. Media beds or large containers (15 L) with loose substrate. EC 1.5-2.5 mS/cm. pH 5.5-6.5. Temperature: 12–20°C (cool highland climate; heat above 28°C suppresses tuber formation). Moderate light (DLI 12-18 mol/m2/day). The critical challenge at temperate latitudes: oca only forms tubers when day length drops below 12 hours (typically October-November in the northern hemisphere), but the plant needs to be large and established by then to produce worthwhile tubers. Start early (March-April) and grow through summer to build a large plant, then hope for a long enough frost-free autumn for tuber formation. In mild-winter areas (zones 8+), this works. In cold climates, frost kills the plant before tubers develop fully. Growing under artificial short-day conditions (covering plants to limit light hours starting in August) is an experimental workaround. Harvest after foliage dies back from frost, digging carefully. Cure tubers in sunlight for 1-2 weeks to sweeten them.

Further reading

• Best crops for hydroponic beginners
• The Kratky method: grow lettuce with zero electricity