New Zealand

Cultivation Break

Season Overview

Description

Ocas are not only the most popular food in the Andes after the potato, they have also been cultivated on a large scale in New Zealand since 1860. They are called yams there even though they are not real yams. This variety originates from New Zealand. The tubers are yellow with red, yolk-yellow on the inside. When eaten raw, you can taste the lemony note (oxalic acid). They taste crunchy and juicy. When cooked, they become softer and more floury, and the acidity is no longer noticeable. Oca (Oxalis tuberosa) is a plant species from the genus wood sorrel (Oxalis) in the family Oxalidaceae, which is native to the Andes in South America. The plant is also known as Andean potato, tuberous clover or Uqa, Oka, Yam or Peruvian wood sorrel. Oca originally comes from the Andes, where it is also cultivated at altitudes of 1500-2500 m and is the oldest cultivated tuber plant in the Andes. Beyond the Andes, the tuberous wood sorrel - still the second most important tuber crop after the potato in its area of origin - has been able to establish itself in Mexico in particular and, interestingly, since the 19th century also in New Zealand. In New Zealand, the oca is somewhat misleadingly called New Zealand yam. Oca is a beautiful plant with reddish shoot tips and shoot axes as well as tubers with different bright colors and shapes. The tuberous wood sorrel is a perennial, succulent, herbaceous plant. It grows to over 30-40 cm high. The roots form strongly branched rhizomes, the tips of which swell into fleshy tubers. The waxy, more or less wrinkled, cylindrical to ellipsoid or club-shaped tubers, with notched "eyes", are 3-15 cm long, white, green, orange, pink, red or purple. The upright or prostrate, fleshy stems are up to 1 cm in diameter. They are dark green to purple in color and usually densely covered with downy hairs. The somewhat translucent leaf stalks, divided at the base by a "joint", are spread out and 7 to 10 cm long. The alternate leaves are divided into three fleshy leaflets. These are obovate with entire margins, about 25 × 22 mm in size, green to purple and have downy hairs at least on the underside. The leaflets are sensitive to touch. Oxalis tuberosa has three different flower types per plant. The inflorescences appear as umbels. The stalked, hermaphrodite flowers with a double perianth are five-petaled. The yellow flowers are up to 2 cm in diameter. The petals with striped sap marks are obovate. Small and one- to few-seeded capsule fruits are formed, albeit only rarely. The seeds have an explosive seed coat which ejects them from the fruit. As a result of intensive cultivation of the species, probably for more than a thousand years, many varieties have developed. With the aim of producing larger, more nutritious and tastier tubers, little value was placed on the flowers of the plants during breeding, resulting in varieties that are no longer able to flower or are sterile and can only be propagated via the tubers. In particular, the varieties with yellow and red tubers are sterile. Young leaves and shoots contain oxalic acid, which gives them their sour taste, usually only in small quantities so that they can be used as a salad or vegetable. The tubers contain significantly less oxalic acid, but starch and larger amounts of vitamin C. If the tubers are exposed to sunlight for a few weeks after harvesting, the acidity largely breaks down and the tubers become sweeter. The combination of the newly deposited sweetness with the acidity then results in a very special fruity taste.

Growing tips

🌼 Pre-breeding - Most varieties in Europe rarely or never flower. - Even when they do flower, they rarely set seed. - Seed production is genetically complicated - many plants are sterile or incompatible. - Oca is almost always propagated vegetatively via tubers. - If you actually have seeds (e.g. from breeding projects or swap meets), this is the way to go: - Light germinate - Sprinkle moist potting compost - Temperature: 15-20 °C - Germination time: 2-6 weeks, sometimes longer - Young plants are tender at the beginning, grow slowly. - Plenty of light, no direct full sun. - Treat later like pre-grown tubers. - Plants from seed are genetically different - so you will get new varieties. 🌱 Planting - Planting time: April-May, as soon as there is no threat of heavy frost. - Planting depth: approx. 5-10 cm. - Spacing: 30-50 cm. 🌤️ Location & climate - Cool, humid climate, does not cope well with heat. - A semi-shady to sunny spot is ideal, avoid direct summer heat. 🪴 Soil - Loose, rich in humus, well drained. - Slightly acidic soils. - Avoid waterlogging at all costs. 💧 Care - Water regularly and moderately. - Mulching helps to retain moisture and suppress weeds. - Oca grows slowly. 🧪 Fertilization - It is best to incorporate mature compost in spring. - Amount: about 2-3 liters of compost per m². - Alternatively: well-rotted manure, but sparingly. - Even nutrient supply during growth. - A light top dressing after 6-8 weeks is sufficient: ◦ Plant manure (e.g. nettle) heavily diluted ◦ Or a small amount of slow-release organic fertilizer (e.g. pellets) - No high nitrogen applications (blue corn, fresh manure, too much liquid manure). - leads to too much green and few tubers. - Do not over-fertilize ❄️ Harvest - does not form tubers until October/November. - Harvest after the first frost, but before the ground freezes through. - Allow the tubers to dry in the sun for a few days - this makes them sweeter. 🌱 Tip for your bed Oca grows for a long time and forms tubers late in the year. Good neighbors are therefore plants that are harvested early or do not root deeply. 🐛 Pests - Snails (young plants) - Wireworms - Aphids - Voles 🍂 Diseases - Powdery mildew (true or false) - Root rot - Virus diseases 🌿 Good neighbors - Cabbages (broccoli, kohlrabi, kale) - Beans & peas - Lettuce, spinach - Onions & garlic, chives - Dill, coriander, parsley - Corn - Sunflowers 🚫 Bad neighbors - Potatoes - Sweet potatoes - Jerusalem artichoke - Root parsley, parsnips - Radish - okra - Other Oxalis species - Tomatoes, pumpkin, melon

Details

Light requirement

Semi-shaded

Water requirement

Moist

Soil

Light (sandy)

Nutrient requirement

Medium

Light germinator

Germination temperature

15 - 20 °C (Degrees Celsius)

Plant distance

30 cm

Row spacing

40 cm

Seeding depth

8 cm