Wondering what they taste like and whether they might be a good addition to a paleo/primal diet. Seems like tubers could be a decent non-grain staple that could be home-grown - I'm considering growing them next year. Apparently they are similar to potatoes: http://www.realseeds.co.uk/unusualtubers.html
I have tried both of these actually, only one time and in the same meal! I noticed on the site it says they are from South America- my mom remembers having these as a kid in Hawaii, not sure if they are popular there or if it was just my mom's foster parents that were into them! When we visited her foster parents in Hawaii a couple years ago, they cooked these for us, along with some other tubers and, of course, pork.
I particularly liked the oca, we had it boiled with roasted garlic and olive oil, there was definitely a lemon-y flavor to them, the combination of lemon/garlic/olive oil reminded me of a greek potatoes dish roasted with lemons. Very good, they were very memorable! Very potato-y texture, but of course the lemon. If you like sorrel, you will like the flavour of oca.
The yacon was very crunchy and quite sweet, reminded me of the texture of water chestnuts or jicama. This one was less memorable for me, but my mom said it was one of her favourites (she's nuts for water chestnuts too), they used to have it in stir fries with bok choy all the time when she was little.
Oca is delicious.
I grew it for about three years in a row but haven't this past couple, I'll need to get back to it.
The plants can be hilled up like you do for potatoes to get more tubers.
The BIG trick after harvesting (when the plants have died back) is to expose the tubors to light for 10 days or so. I leave them on a tarp on our veranda. This makes a huge difference to the taste.
It's a very simple and easy plant to grow, you just need to find a place in your country to order the seed tubers from.
Yacon is a tubur and relative to the sunflower and Jerusalem artichoke.
You might want to avoid yacon syrup which has high fructose like agave!
Also for those avoiding FODMAPS - some people have issues with fermentable oligosaccharides like Yacon
But otherwise the tuber seems okay to eat from time to time.
The fructose content in the tuber appears to be under 20% http://www.bulbnrose.org/Heredity/sunflowerXchoke/sunflowerXchoke.html
Oca are widely available here in New Zealand, where very confusingly we refer to them as "yams" -- blame the dude who introduced here from South American decades ago. You can boil, steam or roast them. Nice kinda nutty flavour, texture is firm, interesting colours, and I believe they're high in vitamin C. Go for it, I say.