Polytunnel growers tend to stick to the same common plants. But one of the great things about a polytunnel is that it can allow you to branch out and grow some more interesting and unusual things. If you are looking for something more unusual to grow in your polytunnel, then these unusual tubers might be well worth considering. Some may be more familiar than others, but all could be fun and interesting additions to your home-growing repertoire.
Why Grow Unusual Tubers in Your Polytunnel?
First of all, increasing the range of plants that you grow is always a good idea. The more diverse your plant selections, the more chance there is that you will get some great harvests later in the year. It is a good idea not to put all your eggs in one basket.
Tubers are enlarged structures in some plant species used as storage organs for nutrients. They store energy for a plant, and they can be a good energy source for us too.
In the UK, of course, potatoes are the most common and best known edible tubers we have. But potatoes do take up quite a lot of space in a garden. And no matter how much you love potatoes – it is possible to have too much of a good thing. Growing some more unusual tubers can allow you to ring the changes and find some other food sources to try.
If you have already branched out, you might have tried to grow root tubers in your polytunnel. You may, for example, already have grown some sweet potatoes where you live.
Jerusalem Artichoke (Helianthus tuberosus)
Perhaps the most familiar of the unusual edible tubers on this list, my first suggestion for an unusual tuber is Jerusalem artichoke. Jerusalem artichokes are easy to grow. They like a sunny spot and will be most productive when grown in a rich and fertile soil. During the summer the plants will grow unobtrusively in your polytunnel (though they will not usually flower in the UK) , and you can harvest tubers after the first frosts of winter. The tubers can be used in the same ways as potatoes.
Maximilian Sunflower (Helianthus maximilianii)
This is another member of the sunflower family that also produces edible tubers but which is less well known. Like the above, they thrive in a sunny and fertile spot, and like Jerusalem artichokes, they produce edible tubers. They do have a lower yield, but the tubers are similar in flavour. These will, however, often flower in a polytunnel in the UK, and so can also bring other benefits to your garden. The flowers attract butterflies, and a range of other beneficial wildlife.
This is another interesting flowering perennial that also produces edible tubers. Known as a Chinese artichoke, this plant is in leaf from May to November and in flower (though only rarely in the UK) in the summer months. The tubers, which can be enjoyed raw or cooked, are around 5-8cm long and about 2cm wide. They can be rather fiddly to harvest. But they do have a mild, pleasant flavour and are somewhat easier than the above options to digest. They have a slightly nutty, artichoke like flavour.
Oca (Oxalis tuberosa)
You may have heard of oca, but not realised that with a polytunnel, you could grow some here in the UK. They require a site in full sun, and a moist yet free-draining soil. When first harvested, the tubers have a sharp, acidic, lemony flavour, but if they are left out in the sun, the tubers turn sweet. Whether in their acid or sweet state, the tubers are delicious and, again, can be used in the same way as potatoes. The tubers of good-sized specimens can reach 8cm or more in length, though they are usually smaller. Tubers do not begin to form until after the 21st of September in the UK. if there are early frosts in the autumn, yields will be low. Growing in a polytunnel can extend the season and make it more likely that you will be able to successfully grow this crop.
Yacon (Polymnia edulis)
Yacon is another South American tuber that could potentially be grown with the aid of a polytunnel here in the UK. It is frost tender and requires a growing season of 6-7 months. But taking on the challenge could be interesting for UK growers. The large tubers are crisp and juicy, and, in some regions, are eaten more like fruits than roots. Like artichokes, this tuber is rich in inulin, which can make it difficult to digest. But this also makes it a healthy choice since it can fill you up without making you put on weight.
The chufa, or tiger nut, is a perennial tuber that prefers a moist or wet soil in full sun. The var. sativus cultivar produces somewhat larger tubers. The tubers are extremely difficult to find, and attractive to mice. But if you can find and harvest them before other creatures find them, you will discover that they are delicious, with a nut-like flavour. They can be dried, and eaten as is, or ground into a powder and used in confectionery.
Mashua (Tropaeolum tuberosum)
Mashua is a tuber that has been cultivated by humans for thousands of years. Also known as Anu, these tubers have a peppery flavour that not everyone favours. But freezing them after they have been cooked improves the taste, and they are then considered to be a delicacy by many people. The tubers can be up to 10cm long and 5cm wide, and are high in vitamin C. The dried tuber has up to 16% protein. To grow it, you will need a well-drained and lime-free soil in a warm and sunny spot. A polytunnel to extend the length of the growing season could make it possible to successfully grow mashua here in the UK.
The ground nut is a very useful plant. Not only does it produce tubers with a very pleasant nutty and sweet taste, it also belongs to the legume family and is a nitrogen fixing plant. So it can help to add fertility to your polytunnel growing areas and enrich the soil. As a climbing plant, this will not take up a lot of space in your polytunnel, and so while the yield will not be huge, it may be worthwhile experimenting to see whether or not you can grow it where you live.
Pig Nut (Conopodium majus)
This native hedgerow plant is in flower from May to June and seeds ripen from July to August. While it can also grow in semi-shade, it can also cope in a full sun spot. You could consider growing it in or around your polytunnel. The tubers have a flavour somewhere between a sweet potato and a hazelnut. But you’ll only get one per plant and they are difficult to harvest. Still, this could be another unusual tuber to consider cultivating in your garden.
Cinnamon Vine (Dioscorea polystachya)
Also known as Chinese yam, the tubers of this plant are another potato substitute. It will grow in a sunny spot and prefers well-drained soil. As well as producing tubers below the ground, this plant also produces aerial tubers, or tubercles. The below ground tubers are difficult if not impossible to dig up. So this may be more of a novelty than a staple crop. But another reason to grow this in your polytunnel is for the intense cinnamon scent that is given off by the plant when it is in flower.
Japanese Yam (Dioscorea japonica)
Easily grown in a fertile well-drained soil in a sunny position or light shade, this climber prefers a rich light soil and cannot grow in the shade. Like the above, this plant also produces tubercles, as well as potato-substitute tubers below the ground.
These are just a few unusual tubers that you might like to experiment with growing in your polytunnel. If you are rather bored with potatoes, or just want to expand your growing efforts, this could be a good route to take.
Do you grow unusual tubers in your polytunnel? Let us know in the comments below.
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.
To get in touch, visit https://ewspconsultancy.com.