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Oxalis tuberosa
  • Oca

a perennial herbaceous vegetable of the Oxalis genus in the family Oxalidaceae. An important crop in the Andes of South America but with a few exceptions it is not grown commercially elsewhere in the world despite it's potential.

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Niche
  • Herbaceous
    Herbaceous
    Small non-woody plants whose above ground parts die at the end of the growing season.
  • Soil surface
    Soil surface
    Plants which grow close to or at soil level, not necessary providing a ground cover function.
  • Rhizosphere
    Rhizosphere
    Plants which exhibit an important aspect in the area inhabited by plant roots.
Functions
  • None
    None
    There are no functions defined for this plant. Do you know of some? Click the edit button to add them!
Light
  • Full sun
    Full sun
    The amount of sun exposure that a plant prefers in ideal conditions.
    Key
  • no shade
    No shade
    The amount of shade a plant will tolerate without adverse health affects.
    Key
Water
  • Water Requirementsmoderate
    Moderate
    The amount of water a plant needs for healthy growth, relative to other plants.
    Key
Soil
  • acid, neutral, alkaline
    Acid to Alkaline
    The PH range (acidity or alkilinity) of the growth medium ideal for healthy nutrient absorbtion.
    Key
  • Sandy to Loamy
    The soil texture this plant prefers for optimal growth.
    Key
Cold & Heat
  • 7
    Zone 7
    The USDA Hardiness scale assigns plants a number from 1 to 12 representing the minimum temperature a plant can survive.
    Key
    0< -53.9ºC< -65ºF
    1-51.1ºC-60ºF
    2-45.6ºC-50F
    3-40ºC-40ºF
    4-34.4ºC-30ºF
    5-28.9ºC-20ºF
    6-23.3ºC-10ºF
    7-17.8ºC0ºF
    8-12.2C10ºF
    9-6.7ºC20ºF
    10-1.1ºC30ºF
    114.4ºC40ºF
    12> 10ºC> 5ºF
  • ?
    Unknown
    The AHS Heat scale assigns plants a number from 1 to 12 representing the number of days per year a plant requires a temperature exceeding 30ºC (86ºF).
    Key
    11
    21 - 7
    38 - 14
    415 - 30
    531 - 45
    646 - 60
    761 - 90
    891 - 120
    9121 - 150
    10151 - 180
    11181 - 210
    12181 - 210
Oxalis tuberosa has 4 edible uses listed

Botanical description

Oxalis tuberosa (Oxalidaceae) is an herbaceous perennial plant that overwinters as underground stem tubers

Uses

Toxic parts

Whole plant, Leaves, Tubers

Oxalic acid, Oxalate low toxicity

The leaves contain oxalic acid, which gives them their sharp flavour. Perfectly all right in small quantities, the leaves should not be eaten in large amounts since oxalic acid can bind up the body's supply of calcium leading to nutritional deficiency. The quantity of oxalic acid will be reduced if the leaves are cooked. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take especial caution if including this plant in their diet since it can aggravate their condition[12].

Varieties of this plant are grouped into those which have sweet tubers and sour tubers. The tubers of the sweet varieties contain less oxalic acid[4].

Edible uses

Tubers

Fresh, Cooked

The tubers of some cultivars may contain high levels of oxalic acid, especially when raw. See the toxicity notes for more information. Edible raw or cooked[1][2][3], they have an acid lemon flavour when first harvested, but if left out in the sun the tubers turn sweet[3] as the organic oxalic acid in the skin breaks down with exposure to sunlight[4], so sweet in some cultivars that they are said to resemble dried figs and are sold as fruits in local markets in South America[5][6][7][8].

The cooked root is delicious whether in its sweet or acid state, it can be boiled, baked etc in similar ways to potatoes[K]. They do not need peeling. The cooked flavour is like slightly lemony potatoes and they are superb served with butter or oil[9]. The tubers tend to be rather smaller than potatoes, with good sized specimens reaching 8cm or more in length. They contain about 70 - 80% moisture, 11 - 22% carbohydrate, 1% fat, 1% fibre and 1% ash[8]. The carbohydrate is rich in sugar and easy to digest[8]. Acid types are rich in oxalic acid (up to 500ppm) but sweet forms have much less oxalic acid than is found in potatoes[8].

See the associated crop notes for the tubers for more information.

Dried, Frozen as a Flour

When the tubers are dried, frozen and cleaned, a storable product named okhaya is produced which can be used as a flour used in the preparation of porridges and deserts[11]. See the crop notes for the tubers for more information.

Flowers

Fresh, Cooked

The flowers can be eaten raw or cooked[5][6][2]. Poor quality[10]. Use in moderation, see notes on toxicity.

Leaves

Fresh, Cooked

The young leaves can be eaten raw or cooked[5][6][2]. One source claims they're of poor quality[10].

Material uses

There are no material uses listed for Oxalis tuberosa.

Medicinal uses(Warning!)

There are no medicinal uses listed for Oxalis tuberosa.

Ecology

Ecosystem niche/layer

Herbaceous, Soil surface or Rhizosphere

Ecological Functions

Nothing listed.

Forage

Nothing listed.

Shelter

Nothing listed.

Propagation

Oca is usually propagated vegetatively by planting whole tubers. Propagation by seed is possible but is rarely used in practice. Sexual propagation is complicated by several factors. First, like many other species in the genus Oxalis, oca flowers exhibit tristylous heterostyly and are consequently subject to auto-incompatibility. Furthermore, on the rare occasion that oca plants do produce fruit, their loculicidal capsules dehisce spontaneously, making it difficult to harvest seed. Oca flowers are pollinated by insects (e.g., genera Apis, Megachile, and Bombus). Data regarding the frequency of volunteer hybrids and farmers? subsequent incorporation of them has not yet been published[4].

Seed

Best sown as soon as it is ripe in a cold frame. Prick out the seedlings into individual pots when they are large enough to handle and plant them out in late spring or early summer.

Rooted cuttings

Basal cuttings in spring[8]. Harvest the shoots with plenty of underground stem when they are about 8 - 10cm above the ground. Pot them up into individual pots and keep them in light shade in a cold frame or greenhouse until they are rooting well. Plant them out in the summer.

Bulb

Put the tuber horizontal, 10cm deep, in easy soil. Spacing 50cm by 75cm[9].

Cultivation

Prefers a light rich soil in a warm sunny position[13][6][8]. Tolerates a pH range from 5.3 to 7.8[8]. Plants succeed in areas with an average rainfall ranging from 570 - 2150mm per year[8]. Oka is widely cultivated in the Andes for its edible tubers, there are many named varieties[10][7]. This species has an excellent potential as a major root crop in temperate zones, it has the potential to yield as highly as potatoes but does not have the susceptibility to pests and diseases that are a bugbane for potato growers[K]. Plants are slightly more hardy than the potato, tolerating light frosts but the top-growth being severely damaged or killed by temperatures much below freezing. The main drawback is that development of the tubers is initiated by the number of hours of daylight in a day. In Britain this means that tubers do not begin to form until after the 21st of September and, if there are early frosts in the autumn, yields will be low[6]. There are possibly some forms in southern Chile that are not sensitive to daylength, these will be more suitable to higher latitudes such as Britain[8]. The varieties that are usually cultivated in New Zealand are daylength neutral. It is said that the varieties with white tubers are bitter because they contain calcium oxylate crystals whilst those with tubers that are of other colours are sweet[7]. Yields tend to average about 7 - 10 tonnes per hectare but experimentally yields of 40 tonnes per hectare have been achieved[8]. Earthing up the growing stems as they start to form tubers can increase yields significantly[8].

Crops

Tubers

Harvest

Tubers begin growing when day lengths begin to shorten. Harvest after the frosts have killed off top growth. The tubers are reported to continue making significant growth after the above ground parts have been killed off, so take care not to harvest too early[14]. They form in a clump close to the centre of the plants. Take care not to damage tubers as you dig them.

Yields of at least 500gr. per plant should be obtained[9], although yields vary with the cultural method. Annals from Andean countries report about 7-10 tons per hectare for Oxalis tuberosa production. But with adequate inputs and virus free propagation material, oca production can range from 35 to 55 tons per hectare[4].

Processing

Tubers of the sour cultivars are traditionally processed to form a usable storage product, called khaya in Quechua. To prepare khaya, tubers are first soaked in water for approximately one month. They are then left outside during hot, sunny days and cold, freezing nights until they become completely dehydrated.[4]. If it is washed after freezing, a whiter product called okhaya is obtained which is considered to be of superior quality.

Storage

The tubers can be stored in a cool, dry environment, much the same as for Solanum tuberosum (Potato). They can also be processed into a product named khaya, see processing notes for further information.

Problems, pests & diseases

Associations & Interactions

There are no interactions listed for Oxalis tuberosa. Do you know of an interaction that should be listed here? edit this page to add it.

Polycultures & Guilds

There are no polycultures listed which include Oxalis tuberosa.

Descendants

Cultivars

Varieties

None listed.

Subspecies

None listed.

Full Data

This table shows all the data stored for this plant.

Taxonomy
Binomial name
Oxalis tuberosa
Genus
Oxalis
Family
Oxalidaceae
Imported References
Edible uses
[1][2][3][5][6][7][8][10]
Medicinal uses
Material uses & Functions
Botanic
[15]
Propagation
Cultivation
Environment
Cultivation
Uses
Edible uses
  • Tubers (Fresh Cooked)
  • Flowers (Fresh Cooked)
  • Leaves (Fresh Cooked)
  • Tubers (Flour)
Material uses
None listed.
Medicinal uses
None listed.
Functions & Nature
Functions
Provides forage for
Provides shelter for
Environment
Hardiness Zone
7
Heat Zone
?
Water
moderate
Sun
full sun
Shade
no shade
Soil PH
acid, neutral, alkaline
Soil Texture
sandy, loamy
Soil Water Retention
well drained
Environmental Tolerances
    Ecosystems
    Native Climate Zones
    None listed.
    Adapted Climate Zones
    None listed.
    Native Geographical Range
    South America
    Native Environment
    Andes
    Ecosystem Niche
    Herbaceous, Soil surface, Rhizosphere
    Root Zone Tendancy
    None listed.
    Life
    Deciduous or Evergreen
    ?
    Herbaceous or Woody
    herbaceous
    Life Cycle
    perennial
    Growth Rate
    moderate
    Mature Size
    0.45 x 0.3 metres
    Fertility
    self sterile
    Pollinators
    insects
    Flower Colour
    ?
    Flower Type
    hermaphrodite











    References

    1. ? 1.01.1 Hedrick. U. P. Sturtevant's Edible Plants of the World. Dover Publications ISBN 0-486-20459-6 (32202/01/01)
    2. ? 2.02.12.22.3 Haywood. V. H. Flowering Plants of the World. Oxford University Press ISBN 0-19-217674-9 ()
    3. ? 3.03.13.2 Facciola. S. Cornucopia - A Source Book of Edible Plants. Kampong Publications ISBN 0-9628087-0-9 (32202/01/01)
    4. ? 4.04.14.24.34.4 [Oca] Wikipedia (2013/05/21)
    5. ? 5.05.15.25.3 Harrison. S. Wallis. M. Masefield. G. The Oxford Book of Food Plants. Oxford University Press (32202/01/01)
    6. ? 6.06.16.26.36.46.5 Thompson. B. The Gardener's Assistant. Blackie and Son. (32202/01/01)
    7. ? 7.07.17.27.3 Towle. M. A. The Ethno-Botany of Pre-Columbian Peru. ()
    8. ? 8.008.018.028.038.048.058.068.078.088.098.108.11 Popenoe. H. et al Lost Crops of the Incas National Academy Press ISBN 0-309-04264-X (32202/01/01)
    9. ? Cite error: Invalid <ref> tag; no text was provided for refs named HowToGPV
    10. ? 10.010.110.210.3 Organ. J. Rare Vegetables for Garden and Table. Faber (32202/01/01)
    11. ? J.E. Hernándo Bermejo and J. León [Neglected Crops: 1492 from a Different Perspective] Purdue University (2013/05/21)
    12. ? Bown. D. Encyclopaedia of Herbs and their Uses. Dorling Kindersley, London. ISBN 0-7513-020-31 (32202/01/01)
    13. ? F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956 Oxford University Press (32202/01/01)
    14. ? [Oca Instructions] The Real Seed Company (2012/12/21)
    15. ? Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press ISBN 0-333-47494-5 (32202/01/01)




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