Grown organically at KoruKai Herb Farm, Banks Peninsula. Free from synthetic fertiliser, pesticides and herbicides.
You will receive 1 large tuber (left hand) or two medium tubers (right hand). The large tuber can be cut in half before planting (more info below).
Mashua has long twining stems on which three to five lobed leaves form. In the autumn, mashua forms trumpet shaped orange, orange and yellow, or occasionally red flowers.
It is an attractive plant and grows up to at least 2.4 to 3.6 m tall if given something to climb. They are fast growing in cool, wet weather and are generally able to out-compete and smother weeds. They do very well in our food forest system.
Underground, the plant forms tubers that reach 8-20 cm in length. The tubers have a shiny, waxy skin that cleans easily. Tubers cluster relatively closely under the base of the plant. Most mashua varieties have predominantly white tubers, although yellow, orange, red, and purple tubers are formed by some varieties. Given a long enough frost free autumn, plenty of water, and an overall cool climate, mashua can produce very high yields. We average 4 kgs per plant. but have had one give us 6.7 kilos this season. Warm climate yields are smaller, reaching around 1-2 kg per plant.
Growing Conditions
Mashua is traditionally grown at elevations of 3000 to 3700 m, where the average annual temperature is 11 C. It is poorly adapted to warm, dry conditions and so is best suited to the South Island of New Zealand, but can also perform well in a food forest situation with some shade and water in summer in the North Island. It thrives in climates with cool summer temperatures, where the high temperature rarely rises above 27 C. It needs consistent water and will benefit from a drip system in climates where rainfall is not regular.
Mashua can be grown on trellis or on the ground.
The plant grows best in full sun in the south of the South Island. Where temperatures frequently exceed 27 C, mashua will grow best in an area that has afternoon shade. In dry climates, it is important to give mashua some wind protection, since dry winds will rob it of water faster than it can replace it.
The plant has some resistance to light frosts, but a hard frost will kill the foliage completely. Because tubers form in the fall, this makes it unsuitable for locations with frosts that occur earlier than the beginning of May.
Planting and Management
Mashua thrives even in relatively poor soils, but loose, light soils benefit you at harvest time. Some vermicast and compost should provide mashua sufficient nutrition. Mashua appears to have a wide range of soil tolerance.
Given another plant or structure to climb up, mashua can grow 2-4m tall. Otherwise it will trail as a groundcover. It can work well climbing up corn in the vege garden, or up trees and shrubs in a food forest.
A reasonably long frost-free autumn is also required as the tubers do not start to set until day length drops below 14 hours. Plants will tolerate a light frost but a heavy frost will kill the leaves and damage the tubers.
Plant whole tubers about 5 cm deep at the end of winter or early spring. Mashua tubers can be cut for more plants, similar to potatoes, ensuring each piece has at least two eyes. If cutting tubers, allow them to heal in a humid environment for a few days before planting. Orientation of the tuber doesn’t seem to matter. We usually plant them horizontally, but tubers are found in a jumble at harvest, so there is probably no right or wrong way to plant them. Cover with a thick layer of organic matter to keep in the moisture and mark the spot.
Mashua is typically hilled up at least once during the growing season. At a minimum, this provides some protection to the tubers, which often grow up and out of the soil. It may also improve yields.
Mashua will definitely benefit from hilling up or mulching if you are at risk of frost before harvest. It has a habit of piling up tubers right at the surface and these will be ruined in a frost if they are not protected. They will also turn green from exposure to the sun, which does not affect edibility, but can look less appealing.
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Harvest
Tubers are harvested in the early winter when the tops of the plants begin to yellow and die back. The tubers can be dug up, cleaned, and stored in a cool, dark place. They can also be left in the sun for up to a week to develop a sweeter flavour if required. Choose the best for replanting and eat the remainder.
Uses and Nutrition
Mashua tubers are high in vitamin C and relatively high in protein for a root crop. The vitamin C content may vary significantly with variety and growing conditions. Some measurements of vitamin C content in mashua are as high as 120mg/100g, which is more than twice as much as an orange and comparable to an equal weight of kale. Mashua contains large amounts of glucosinolates (mustard oils) and, as a consequence, isothiocyanates. Isothiocyanates have antibiotic and insecticidal properties, making them a great companion crop. They also appear to play a role in carcinogen detoxiification and/or promotion of apoptosis in pre-cancerous cells.
Like garden nasturtiums, mashua leaves can be used in salads, as green wraps, or wilted like spinach. The flowers have large nectaries and are sweet with hint of aniseed flavour, and not as spicy as nasturtium flowers.
The tubers can be eaten raw; they have the crunch and spicy hit of a radish. They can be sliced or grated thinly in salads, used in coleslaw, or pickled. When roasted the tubers take on a creamy texture and the flavour is strong but sweet with a hint of licorice and vanilla, quite a complex flavour. The tubers can also be chopped and used like potatoes or yams in stews, soups, and curries. Mashua is said to work well in strongly spiced dishes, especially having an affinity with cumin, and can also be cooked with fatty meats to add flavour.
Below: Record harvest! 1 plant yielded 6.7 kilos of tubers.
