Yacon, is an ancient perennial plant originating from South America that is easy to grow, vigorous and almost completely pest-and disease-free. It produces edible tubers that have the texture of water chestnuts, look like a sweet potato and taste like sugar cane, crossed with a watermelon, with slight overtones of pear! These tubers weigh 300-500g, are high in fibre and pretty much calorie free. They also contain oligofructose, a sugar that the body does not metabolise, which makes them highly prized as a sweetener for diabetics. The best thing about Yacon is that it is incredibly hardy, tolerating hot summers, drought and poor soils, although it does best where there is moderate heat (between 10°C and 25°C) and constant moisture. It needs about 200 frost free days to complete its life-cycle so is a perfect fit for the sub-tropics and tropics, but if you want to try growing Yacon in a cooler climate, simply start it off indoors and plant out once the weather warms up.
Yacon apparently does best planted straight into the soil, but given that it prefers rich, loamy soil with good drainage and we are stuck with heavy, infertile, poorly-drained rainforest soil we decided to grow it in half barrels instead. Ideally the plants should be planted about a metre apart, but we paced one plant in the centre of each half barrel and found that worked fine. As the plants can grow up to two metres tall you may want to consider sinking the pots in the ground.
Once the Yacon has been planted out it requires very little attention, apart from weeding and a good watering if the weather turns dry. The main stems can be harvested periodically and used like celery. Yacon matures after 6-7 months and then produces small yellow flowers. The tubers form in Autumn when day length shortens and should be harvested in winter once the plant has finally withered and died back.
To harvest Yacon, carefully dig up the crown using a garden fork, being careful not to break the brittle tubers. Once you have uprooted the plant you will find two types of underground structure. The tuberous roots used by the plant for food storage look like a sweet potato (shown on the left in the photo below) and are best for eating. Then there are rhizomatous roots that make up the ‘crown’ just under the soil surface. These roots have a reddish tinge and look a bit like a Jerusalem artichoke (shown on the right of the photo below). Whilst these can be eaten when young, they quickly become tough and fibrous so are generally better saved for propagation.
Snap off the large storage tubers and then store the crowns in damp compost or sawdust in a cool frost-free place where they won’t dry out. In early spring plant the crowns into large pots and wait for shoots to start growing from each small tuber.
Split the crowns into individual shoots (with their tubers attached) and plant each shoot about 4cm deep in its own pot. The flowers of Yacon do not produce viable pollen or seeds, but if you are looking for other ways to rapidly increase the number of Yacon plants in your garden , tip cuttings can be taken when the tubers sprout in spring.
The large storage tubers are crunchy, tasty and refreshing immediately, but unless you are diabetic they are best if left in the sun for a couple of weeks. During this “Curing” process the non-digestable oligofructose is converted into fructose, glucose and sucrose and this process significantly increases sweetness. Store the tubers in a cool dry place such as a root cellar and they will keep for up to 8 months. Damaged tubers have a much shorter shelf life so should be eaten first. This is our first year growing Yacon and we started with just 4 plants as a trial,which yielded about 25 tubers. As yields tend to increase considerably in the second year and are generally double to triple those of potatoes I am hoping for a bumper crop in 2015!
Once you are ready to eat the Yacon tubers you can use them in either sweet or savoury dishes. The skin is not very pleasant so it is best to peel the tubers before use. Once exposed to the air the flesh will start to turn brown, but drizzling with lemon juice will prevent any discolouration. Yacon is often eaten raw as a snack or shredded into salads, but I have to admit I much prefer it cooked. As Yacon retains its crunch during the cooking process it works especially well in Asian stir fries. It can also be boiled, roasted, baked, incorporated into sweet pies or fried to make healthy chips. I am always looking for new ways to use the fruits and vegetables I grow in the garden so would love to hear from you in the comments section if you have any new Yacon recipes I can try!