Yacon. Photo by Will Bonsai
By Will Bonsall
Years ago in conversations with my Peruvian sister-in-law, I learned about many traditional foods she grew up eating that were not readily found in the United States – things like oca, mashua, ulluco, quinoa, chuño (freeze-dried bitter potatoes), nuñas (popping beans), yacon, etc. Some of them are difficult or impossible to grow here, either because our season is too short and cool or because of “daylength sensitivity” (photoperiodism), which prevents some species from forming tubers, bulbs, fruits, etc., in our long, cool summer days. I had assumed that yacon was among those – one doesn’t hear much about it in northern gardens – until I heard from my friend Larry Forbes and others in the Fryeburg area who were growing it without greenhouses or other season extenders. Fryeburg is no more of a banana belt than where I live in Industry, so I had to give it a try.
Yacon (Smallanthus sonchifolius) is in the Asteraceae family, along with sunflowers, terrasols (sunchokes), daisies, lettuce and chicory. Unlike most of them, it is quite frost-tender, yet like many of them, the underground parts are improved by a light frost aboveground. Actually its underground parts include two types of “roots” that are actually stem tissues: the long, large, edible tubers and the tightly-bunched rhizomes around the bases of the stalks. Several stalks eventually spread from the original seed-piece, forming a clump.
The rhizomes resemble terrasols (aka sunchokes) in being “lumpy” with several “eyes” or growth-points. This in fact is the way to propagate them: Break away each rhizome and plant it, although they can be further cut for more “seed” as long as each seed-piece has at least one growing point. By the time I planted mine, they were already well sprouted, but I could have gotten an earlier start, and thus an even better yield, by starting those indoors. I made my share of mistakes with these, but although some tubers were too small to be useful, plenty were nice yam-sized tubers. They are very crisp and succulent, which I guess explains their name: “yacon” means “water-root” in Quechua.
Because the young plants are very frost-tender, I did not plant them out until early June, but if I were planting dormant (not yet sprouted) tubers, I would have dared to plant them out at least a week or two earlier. Again, unlike those Andean crops that are daylength sensitive, yacons can be started earlier or later; it’s just that too early risks freeze-out and too late means smaller yields. I had read that yacon makes a crop in six or seven months (which is what deterred me from trying them long ago), but I got a fine crop in my cool four months. I assume if those smaller tubers had time to size up better, I would have had a truly bodacious crop – yacon is said to out-yield potatoes by twice.
I spaced mine 2 feet apart in each direction, although I’ve since read that 3 feet each way is better. With more experience I’ll have a surer opinion. Also, my plants grew to be 3 to 4 feet tall, whereas the literature speaks of 6 to 7 feet, which I don’t doubt – especially with an earlier start and more attention to watering. I’ve yet to learn whether yacon would companion well with pole beans the way beans do with my sunflowers and amaranth, but I can’t see why not, especially at the wider spacing. Unlike planting pole beans later than those cold-hardier sunflower and amaranth crops, I assume I would plant pole beans at the same time as yacon.
Once established, yacon is remarkably resilient and pest-free. Although it tolerates drought rather well, steady water and ample humus (preferably not high-nitrogen) will promote larger tubers.
Although its fertility requirements are moderate, yacon definitely prefers deeply-worked soil as you might expect from a heavy-rooted crop. I used a broadfork on a garden bed that was already stone-free. Even then a couple of long tubers broke in half as I lifted them with a spading fork. I was able to retrieve them with a little effort, but next time I’ll use the much deeper broadfork for harvest as well as soil prep.
Supposedly yacon develops small, yellow, daisy-like flowers late in the season; mine did not, but then most of my terrasol varieties don’t usually flower either, except in unusually late autumns. The variety that’s most readily available in this country (with no name that I know of) has off-white tubers, but yacon plants exist in several other tuber colors, including yellow and purple.
Although yacon is grown primarily as a food crop, it’s most touted dietary benefit is its indigestibility. You read that right: its high content of fructooligosaccharides is resistant to breakdown in the stomach, much like the inulin in terrasols. While that might seem like a dubious “benefit,” it is especially useful to diabetics and to those trying to cut calories, since one feels sated before getting overloaded with carbohydrates. For those who, like myself, are not diabetic and have no need to lose weight, it has other benefits: Those same components help keep one’s cholesterol level under control, while the abundant potassium, calcium and phosphorus are good for just about everything. Yacon carbohydrates are also touted as a prebiotic, promoting the growth of beneficial bacteria for a healthy gut. That healthy gut environment also favors greater absorption of many trace minerals. Yacon is also claimed to be rich in anti-carcinogens, which is marvelous, but frankly of more interest to me are its intriguing taste and textures. Its tender-crispness with a distinctive sweet fruitiness is more suggestive of an Asian pear than any other root crop.
The larger leaves are also used as wrappers for various stuffings, much like cabbage leaves in Hungary or grape leaves in Lebanon. I’ve yet to try that.
Yacon syrup is becoming popular in markets. It is used both as a sweetener and for all those health-imparting qualities attributed to the tuber. It seems like it would be easy enough to make your own simply by crushing and pressing the very juicy tubers and then cooking the juice down to a syrup. I shall definitely be trying that.
I’m storing the large tubers in a tight-lidded 5-gallon bucket to prevent withering; the smaller “seed rhizomes” I’m keeping in an open bin in the dampest corner of the root cellar. In fact I’m storing the whole crowns intact – with a bit of stem – and waiting until planting time to break them apart. This is my first year storing them, but that’s the way I received them from Larry, and it seems to have worked very well.
Peel yacon tubers before eating, because the thin skin imparts a bitter-pitchy taste or aftertaste to the otherwise-delightful flesh. By the way, they become even sweeter with storage, although I assume that must be at the expense of their inulin, thus reducing their value to diabetics. I know that is the case with terrasols, whose inulin begins to break down to simpler sugars. Once peeled, yacon tubers are delicious raw (traditionally diced in fruit salads), baked or stir-fried. Like terrasols, they ought not be overcooked. When used raw, it’s good to sprinkle lemon or some other citric juice on them to prevent browning, plus the juice adds a pleasant zip to their bland sweetness (think pears). In Colombia yacon is often combined with pineapple and other fruits in a salad called salpicon.
As I mentioned, I did a lot of things less-than-perfectly: planting a bit late, letting the seed rhizomes get a bit withered before planting, haphazard watering. Despite all that, I got a respectable crop. I assume I can only do better in the future, and considering how hooked I am on that unique flavor, I will definitely be growing them again and again.
About the author: Will Bonsall lives in Industry, Maine, where he directs Scatterseed Project, a seed-saving enterprise. He is the author of “Will Bonsall’s Essential Guide to Radical Self-Reliant Gardening” (Chelsea Green, 2015). You can contact Will at [email protected].