Oca

Sun

Full sun in cool climates; light afternoon shade where summers are hot.

Water

Keep evenly moist but not waterlogged, especially during autumn tuber formation.

Soil

Loose, fertile, well-drained soil, preferably slightly acidic. Avoid compacted ground and sites that stay wet in winter.

Height

1-1.5 ft (0.3-0.45 m)

Spread

2-3 ft (0.6-0.9 m)

Flowers

Small yellow flowers in summer or autumn; flowering is often sparse or absent.

Foliage

Soft, fleshy stems bearing three heart-shaped leaflets; foliage is usually green, sometimes with purple colouring.

Growth

Moderate at first, becoming vigorous in summer.

Care needed

Medium

• Low allergen
• Edible

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.1 ft (0.33 m)

3. After 2 years

   1.2 ft (0.36 m)

4. After 3 years

   1.2 ft (0.38 m)

   full size

About 2 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Growth rate

Fast

• Plant sound tubers 2-3 in (5-8 cm) deep and 12-18 in (30-45 cm) apart after frost danger has passed.
• Work compost into the soil before planting; avoid heavy nitrogen feeding, which encourages excessive leafy growth.
• Water during dry spells and maintain steady moisture as tubers swell in autumn.
• Mulch to conserve moisture and protect shallow tubers from light frost.
• Use horticultural fleece over the foliage during early autumn frosts to extend tuber growth.
• In cold or wet-winter climates, lift the crop and store planting tubers somewhere cool, frost-free and ventilated.

Pruning. Do not routinely trim healthy foliage, which feeds the developing tubers. Remove dead stems after frost has killed the tops, just before lifting the crop.

Lift the tubers in late autumn or early winter after the foliage has died back, but before the soil freezes or becomes persistently waterlogged. If the ground remains unfrozen, waiting a week or two after the first light frost can allow more tuber swelling; loosen the soil with a fork and gather even small tubers. Exposure to daylight for several days in a dry, frost-free place can sweeten the harvested tubers.

Late winter

Check stored planting tubers and discard any that are soft, mouldy or rotting.

Early spring

In short-season climates, start tubers in pots under cover in a bright, frost-free place.

Late spring

Harden off potted plants and plant outside after the last frost.

Summer

Water in dry weather, weed around young plants and mulch once the soil has warmed.

Early autumn

Keep plants watered and protect foliage from light frost while tubers begin swelling.

Late autumn

Lift after the tops die back, before frozen or saturated soil damages the tubers; select sound tubers for replanting.

• Use in a dedicated kitchen-garden bed where its spreading stems can fill the space through summer.
• Plant along a sunny edible border for a low mound of clover-like foliage.
• Grow in large containers on a patio where autumn frost protection and harvesting are easier.
• Follow an early crop of radishes or lettuce with oca, allowing room for its later spread.

Garden styles it suits: Potager (kitchen garden), Edible landscape, Homestead, Cottage garden and Small-space.

Plant it with: Lettuce, Radishes, Spring onions and Calendula.

Wildlife: Flowers, when produced, can provide nectar and pollen for visiting insects. Oca is not a dependable flowering plant for a pollinator border.

• Little or no tuber crop: short autumn days trigger tuber formation, so early frost can stop growth too soon; start plants under cover and protect foliage in autumn.
• Slugs and snails: protect emerging shoots with barriers, hand-picking or locally approved iron phosphate bait.
• Aphids: inspect soft shoot tips and wash colonies off with water; avoid unnecessary insecticide use.
• Tuber rot: improve drainage, avoid saturated soil and store only sound, dry-surfaced tubers in a ventilated, frost-free place.

Oca contains soluble oxalates, particularly in its leaves and stems. Cats, dogs and horses should not eat it: substantial ingestion can cause serious poisoning, including kidney damage. The tubers are an established human food, but their oxalate content varies; boiling and discarding the water reduces soluble oxalates. People with kidney disease or a history of calcium oxalate stones should seek medical advice before eating it, and leaves should not be eaten in quantity.

• Pink wood sorrel (Oxalis debilis)

  It has similar three-part leaves but usually conspicuous pink flowers and clusters of small bulbs rather than oca's elongated, knobbly edible tubers.

• Bermuda buttercup (Oxalis pes-caprae)

  It also has yellow flowers, but its leaves arise mainly from a basal clump and it grows from bulbs and bulbils rather than oca's swollen stem tubers.

• White clover (Trifolium repens)

  Its rounded leaflets often carry pale chevron markings, and its white flowers form rounded heads. Oca has distinctly heart-shaped leaflets and individual yellow flowers.

Oca comes from the Quechua name uqa; Oxalis refers to the sour taste associated with the genus, and tuberosa means tuber-bearing.

Propagation. Save healthy tubers and replant in spring, either directly after frost or first in pots under cover. Small tubers left in the soil may regrow where winters are mild; seed is uncommon and does not reliably reproduce the parent plant.

Accepted botanical name

Oxalis tuberosa

Native range

Argentina Northwest, Bolivia, Colombia, Ecuador and Peru.

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.