Short version:

A perennial root vegetable that has juicy tubers that look like sweet potatoes, felty leaves and small daisy like, yellow flowers. They are harvested in December and have the texture of water chestnuts and the taste of the inner sweet core of carrots (according to a friend). They grow from the rhizomes rather than the tubers. Tubers contain inulin and become sweeter if left for a week on a sunny windowsill.

December is a good time to talk about yacon. As the frosts arrive, the yacon plants are shrivelling. They are a little-known, perennial root vegetable (in the UK anyway). I had only heard of it a couple of years ago as I strove to make my garden more perennial. So – like potatoes, yacon roots will swell to form tubers for winter storage, unlike potatoes which propagate from these tubers, the yacon also has rhizomes which will grow shoots in spring to form the new plants. I’ve read that the tubers also can be used to grow plants – but if you have these much less tasty rhizomes there for propagation, why would you not eat the tubers?

I’m not overly fond of perennial root vegetables, if I’m honest, as it requires more work than I like. For me, the perfect plant is one I plant one year and then for ever after (or at least for many years after) I get to harvest something from them. I don’t mind if it takes a couple of years for something to get going, but once it’s going, I prefer to pick fruit, leaves, nuts, stems… basically something that doesn’t require pulling up and replanting every year. I love low maintenance self-seeders too, like winter purslane or nasturtiums.

Young (ish) yacon plants at the top of the planter in early June. There’s strawberries in the front, a tromboncino behind on the left that had space to grow over the fence and some sugar snap peas that grew and were harvested before the yacon got too tall. The pallet planter itself was filled with around 3 months worth of kitchen green waste and cardboard and left to decompose the winter before.

What does a yacon taste of?

This is the first thing to talk about because this is the reason I grow it, despite my laziness. It isn’t available in the shops and its taste and texture is very unusual. Basically, raw, it has the texture of water chestnuts. For anyone who hasn’t had water chestnuts it’s like a radish, but brittle. Radishes (like carrots) I would call crunchy. Yacon is more, what I’d call crispy – like a crisp apple. Aaaargh! It’s difficult to describe. Now, the taste is something between apple, carrot, pear… celery? Or as my neighbour said – core of a carrot. Someone mentioned a slight honey taste. When freshly picked it doesn’t taste that amazing, but when left to ‘cure’ on a sunny windowsill it turns unexpectedly sweet. The texture gets a little softer, but that’s a price I’m willing to pay for the sweetness. After some cold weather, if left in the ground it also gets sweeter, though not as sweet as those cured on the windowsill. If anyone has the vocab to describe both the taste and the texture please comment. I really am stuck!

From what I’ve read, yacon has a sugar in it called ‘inulin’ which human digestive systems can’t process – so it’s supposed to be great for diabetics and those wanting to lose weight. Just a warning though, if you eat too much you get rather windy. This is because the inulin is instead digested by our gut bacteria creating gases in the intestines. It is, therefore, reportedly good for gut health as a prebiotic (something that feeds the bacteria as opposed to a probiotic which is something that contains lots of healthy bacteria to populate the gut).

Growing yacon

I’ve never seen these available as seeds. They are also not available from the usual companies. They can be found online on websites specialising in perennial vegetables or on eBay. They’re sold as rhizomes or young plants. I suspect young plants are the safer option as you’ll know it survived and rhizomes could’ve been damaged if not stored properly. Rhizomes are easier to send in the post though.

This small plant is then potted into fertile compost when all danger of frost has passed and basically left until the first frosts in winter kill the plant above ground. The more fertile the soil and the sunnier the spot, then the more likely it is that you’ll get many big tubers. They also need sufficient water for lovely juicy tubers. They don’t do well in our clay, stony soil so we only grow them in planters or very (I really do mean very) large pots. They are great for pots though as it makes for an easier harvest.  

The yacon have velvety spear shaped leaves with slightly jagged edges. The stems go purple at the base and the flowers are yellow and about the size of a 50p. Depending on the fertility of the soil and the size of the pot the plant can be 3 to 5ft at maturity. They are also rather bushy.

Harvesting yacon

When the plant above ground is dying you can start harvesting yacon. This year we began at the end of November because I had run out of veg in the house. All you need to do is grasp the bottom of the shoots and gently and slowly wriggle the whole thing out of the soil. The roots are fairly brittle and the skin of the tubers quite delicate, so you need to be kind. When you’ve pulled the while thing out it will be fairly obvious if any of the tubers have broken off and been left in the soil. Alternatively, if they are grown in a pot you can shake the whole pot out and extract the whole root system.

You can stagger the harvesting as the tubers don’t go mushy in the ground after a frost. They can get sweeter with some cold weather. The plan so far is to harvest every 2-3 weeks to keep a continuous supply.

Once the roots are out you snap or cut the tubers off from the rhizomes. The stems and the dead leaves can be cut off the rhizomes and composted. The rhizomes can then be stored in some damp (but not wet) compost till spring. If you’re worried about the winter weather, they can be put into a shed or something. Mine have survived the winter fine outside so far but the winters have been mild here.

In the spring check the rhizomes for any sprouts. You may get several sprouting tips on each rhizome which can be cut into chunks according to sprouting tips and grown as separate plants.    

Storing and eating yacon

Let the yacon dry indoors for a day so the soil dries and can be brushed off with gentle fingertips and place on a sunny windowsill for around a week or two to ‘cure.’ Now, literature says that they shouldn’t be washed as scrubbing damages the skin and leads to mould. What if I didn’t scrub?I believe that they’re fairly damp when they come out of the soil so is there anything wrong with giving them a little rinse immediately after harvesting and patting dry before curing or storing in the fridge? I harvested a batch yesterday morning (12th Dec) and I’m going to try washing them and I’ll post in comments next week the results of washing.

You can eat them fresh, cured or anything in between the two. Curing makes the yacon sweeter (to the extent that it can be as sweet as an apple) but the yacon will be less firm (slightly rubbery to touch but oddly it’s still got that bite when eating) and it’s harder to peel because it’s a little soft.

The skin can be bitter so they should be peeled. The yacon will then discolour, it goes a very dark green (almost black) colour, quite quickly after peeling, especially one that has been cured. They still taste fine though. Because the skin was so thin, one time, I tried just scrubbing them the way you can carrots. This was a bad idea. They were still bitter on the surface and the water went very dark green and I ended up having to peel anyway. Just an FYI, the juice of the yacon feels sticky on your hands and is hard to wash off.

They are very juicy when eaten raw. They’re great chopped into salads. They maintain structural integrity when stewed. They have a pleasant bite when fermented with kimchi in the place of carrots. They can be roasted or sautéed. The absolute winner for me is that my little monkey loves them raw as a snack. Prebiotic veggies into child… that’s a mummy win… and she has no trouble letting one rip when the gas builds up!