Mashua, the nasturtium with edible root tubers

Mashua, or tuber nasturtium

Mashua is a type of root crop nasturtium that was selected by the ancient Incas for its resilience and nutritional value.

Key mashua facts

Botanical nameTropaeolum tuberosum
Common names – mashua, tuber nasturtium
FamilyTropaeolaceae
Type – tuber vegetable

Height – 6 to 10 feet (2 to 3 m)
Planting distance – every 20 inches (50 cm)
Exposure – sun, part shade eventually
Soil – rather light, humiferous, well-draining

Planting – May, June
Harvest – November

Certainly you’ve heard of the peppy ornamental nasturtium that flows through flower beds in the garden, which you might have planted to lure aphids away from the vegetable patch. How about meeting its cousin, the tuber nasturtium? This climbing perennial hails from South America, where it has been grown for generations for its one-of-a-kind tasty tubers.

Note that roots aren’t everything: the rest of the plant, from leaf to flower, will definitely elicit glee from anyone tasting your new nasturtium-filled recipes!

Planting mashua

Preparing the soil

In Fall, prepare your soil with a generous amount of soil amendments such as soil mix, sand for drainage and ashes for potassium nutrients. Indeed, it’s important to note that tuber nasturtium grows best in light, well-draining soil types. In Spring, just before planting, shuffle the soil around in the planting area, adding more compost or fully ripe manure.

Planting

At the beginning of Spring (February, March), plant the tubers in pots and keep these out of the cold. In mid-May, when you’re sure it won’t freeze anymore, set stakes up every 20 inches (50 cm). These should be pretty sturdy, and at least 6 feet / 2m tall to fully support the plant during its vigorous growth. Near each stake, transplant one of the young seedlings. For a better harvest, make sure your seedlings start off in full sun. Since mashua is a very productive plant, just a few specimens will do for the needs of a whole family.

Growing and care

Growing and planting mashuaIt’s pretty easy to care for tuber nasturtium, and it won’t take much time. The main task is ridging, in the same manner as you would ridge potato plants. This will greatly increase the number and size of your tubers. Another point is to stay wary of dry spells, so you can water when the weather is too dry. Last note: no need to prune or trim mashua as it grows.

Diseases and pests

Mashua is more vulnerable to pests and parasites than it is to disease. Among the most common bugs that prey on the plant, you’ll find caterpillars and flea beetles (Epithrix spp.) which tend to devour stems and leaflets on sprouts and adult plants. Like all species of nasturtium, it is highly vulnerable to aphid attacks, especially the black aphid species).

Harvest and keeping

Harvest takes place in Autumn, when leaves have already died off. Unearth the tubers with a spading fork. This reduces the risk of damaging them. A good thing to know is that it’s perfectly possible to simply keep the tubers in place in the ground, and only harvest them when you’re about to consume them. There is a chance, however, that rodents take a nibble at them in this case. To avoid this problem, store your harvest in dry sand and keep it in the dark, away from light.

Cooking with mashua

Cooking with mashuaIt’s possible to prepare and cook mashua tubers in various manners:

  • new leaves will thicken and spice up summer salads;
  • flowers will decorate meals, they also have a peppery taste;
  • the tubers, for their part, are edible both cooked and raw. You’ll be surprised at their chocolatey after-taste.

Smart tip about mashua

When uprooting the plant for its tubers, make sure not to drive the pitchfork too close to the stem, since most of the roots are clustered right around the base.


Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Mashua tuber types by Michael Hermann under © CC BY-SA 4.0
Blooming mashua by Teresa Grau Ros under © CC BY-SA 2.0
Cooked mashua and oca tubers by Håkan Svensson under © CC BY-SA 3.0