I grew this for the first time last year. I wasn’t sure what to expect, because I had never, to my knowledge, seen it growing. Usually these things can turn out a little disappointing, but mashua has been an exception for me. First a little about mashua. It is a plant grown as a food crop in the Andes in South America. Although we tend to think of South America as either desert or tropical jungle, in fact much of it has a similar temperature range to the UK. The altitude keeps it cooler and damper, at least in the west. This means, much like those from the Himalayan valleys, many of the plants find themselves quite at home in Britain. Mashua is a tuberous climbing vine closely related to the nasturtium flower, and all parts of it are edible – tubers, leaves and flowers. It can grow quite tall in a single season, but will die back to the tubers over winter. Typically these tubers don’t start growing until the day length is shorter, which can be a problem in our latitudes, since that is not until later in the autumn and it can run out of growing time, so have a reduced cropping potential. This was also the case for potatoes when first introduced, and daylength neutral varieties of mashua are now available, Ken Aslet being the one usually mentioned.
I got tubers from two different sources, the Agroforestry Research Trust, and Pennard Plants. I’m not sure what variety either of them are, but they look similar at a glance. Because I had so few tubers I decided to plant them in the polytunnel, although unless you are exceptionally exposed, they would probably do fine outside. I used my usual slug protection of a cut off pot, although in my experience they don’t suffer too badly from slug damage. The foliage is bronzed, and similar to a nasturtium leaf, but lobed. If you like nasturtium leaves in salads (which we don’t), you would like mashua leaves. They have a similar peppery flavour. The plants climbed happily up netting, sticks and strings. The individual leaf stalks wrap around in a rather endearing way. Towards the end of the season I did get flowers, but this was so late that they were frosted, and I didn’t get to taste them and there was no chance of seed. I couldn’t see when the tubers started developing, the lower part of the plants being obscured by other vegetation. When the tops died back after the first hard frosts at the end of November, I could see that the tubers were formed by the tips of new shoots burying themselves back into the ground, forming a mass quite close to the plant centre. I think that earlier in the year new growth from the ground forms climbing shoots, and later in the year they form tubers.
When dug up the tubers were of various sizes ranging from very small – an inch or so – to maybe six inches and an inch or more broad. I was impressed by the yield considering I had basically neglected them.
I got one pound of good tubers from one tuber and three pound two ounces from the other tuber, not including some smaller tubers that weren’t worth eating. Since I only grew one of each source, I wouldn’t make any conclusions based on this. It may be that one got more or less watering, or more or less of some nutrient in the soil. If the same happens again on a larger sample I will let them know – apparently they can accumulate virus infections. After planting they got no real attention, except trying to get a bit of water to them, but as usual I struggled with my water supply at various times in the tunnel, so they probably got a bit drier than they would like. Even so the yield was more than I usually manage from potatoes outside, not great by good gardener standards, but pretty good for me! In appearance they are a bit like the smoother sorts of jerusalem artichoke you get – pointy ended and a bit scaley. Creamy coloured with pinkish tinges, they are quite attractive. When tried raw – again they have that spicy radish taste of nasturtiums, and are firm with a crunch. We did not like them raw, but if you are a fan of radish, you might like them in a salad, or grated in a coleslaw. Cooked, the spicy flavour and much of the crunchiness disappears and they become quite bland. One of the plants (the lower yielding one) appeared to be more spicy than the other, again this could be a factor of the way it was grown rather than the variety. We didn’t have a huge amount to eat, because I was impressed enough to want to save the best tubers to grow more this year, but we tried them stir fried with spices, in stews, and pot roasted with other vegetables and meat. S. said he’s happy to eat it again, so we’re sorted. I didn’t tell him that the South Americans regard it as an anti-aphrodisiac. Apparently it may have an effect on sperm count rather than testosterone.
I stored the best tubers in pots of compost in the shed. This was intended to keep them cool and frost free, but since some of the scrappy tubers I planted outside did survive and grow this spring, I may experiment a bit more with that this winter – I didn’t risk any of the good tubers, so am not that upset that several disappeared in the ground over winter. They started to sprout of their own accord quite early in the spring (by Skye standards), so they came out of the shed into the polytunnel to save them getting too leggy. Some were planted out around the garden. I have not given them supports to climb up, since I have read they do not do so in South America, rather left them to scramble over the ground to smother weeds. If I was growing closer to other vegetables, I might give them canes like runner beans. Some I have planted in the polytunnel again, since they did so well last year. I have planted them along the outer edges with netting to scramble up.
So far (end of July) the ones in the tunnel are climbing at crop bar level. They are getting watered when I water the rest of those beds (I have a trickle hose system set up), although I also try and give the corner ones a bit more water, since the hose system doesn’t tend to reach that well into the corners.
The ones outside are more variable. I planted some in the tea garden below the barn, where it is quite open. Two out of the four appear to have been eaten by slugs (I didn’t give them any protection), the other two are still very small. Some of the ones in the dog resistant garden have also disppeared, but at least one is doing quite well and is climbing happily with the beans up the poles. I also planted some in the fruit garden. These seem to be doing better – one of those is one that over wintered. I suppose to be fair, I should have pampered some of those more, although the ones inside haven’t been particularly pampered either. At this stage I can’t say which will do better in terms of yeild. The ones in the tunnel have certainly put on more growth above the ground, and are likely to persist later, having a little more protection from frosts and winds. However the ones outside will get more moisture, which may be more significant….
The only pests I’ve seen is a bit of slug damage, although I have read that like nasturtiums they can get affected by cabbage white caterpillars. Apparently in the autumn, voles can eat the tubers in the ground, but we’ll cross that bridge if we come to it. Overall an exiting new crop for me that appears to tolerate a bit of neglect!