This week UW-Madison ethnobotanist Eve Emshwiller taught me to care deeply about oca, a funky little tuber that I will probably never see.

Botany seems like a conflicted field to me.  Some researchers are working to develop “perfect” varieties of plants that can be grown in vast monocultures, while other botanists are scrambling around the world trying to protect as many different varieties of plants as possible, no matter how “imperfect” they may appear.

Emshwiller described a wheat variety that was collected in 1949 in Turkey. It was called a “miserable” specimen that was not robust and made crummy bread.  Fortunately this pitiful plant was saved in a seed bank where 15 years later it was able to provide resistance to stripe rust that was decimating crops of mainstream monoculture(not “miserable”) wheat.

More recently, the U.S. got a wake up call in 1970 when the Southern Corn Leaf Blight wiped out much of the corn growing in this country.  Some states lost half their crop.  Again, fortunately there were different varieties stored in seeds banks that were resistant.

The list goes on.

And on.

That brings us to Emshwiller’s own botanical underdog – Oxalis tuberosa, native to the Andes in South America. (learn more at the International Potato Center site here.)

International Potato Centre photo credit

...Oca in all its glory. (photo credit: International Potato Center)

Oca looks like a potato at a costume party, and even Emshwiller says that it is an acquired taste.  One type is described as having the sweet, sour, tart flavor similar to baked apple.

The other traditional type has so much oxalic acid ( a toxic substance often used as a rust remover) that it must be soaked in a stream and then dried in the hot mountain sun and frozen in the cold Peruvian nights, till the shriveled remains look like something you pick up when you walk your dog.  Its best attribute is that it stores well in this dessicated condition.

You have probably never tasted one, and you probably never will.  Emshwiller had tried to grow oca in the UW greenhouse, but oca only produces in the precise light found in the Andes.  No one exports them from South America.  They don’t even show up in local Peruvian markets.

Peruvians use oca as a rotation crop with their staple, potatoes.  Because you can’t keep growing potatoes in the same soil year after year, they alternate with oca.  It’s a system that has worked for thousands of years.


...Peruvian mountains (photo credit First Rooz at Flickr)

You would think oca would be safe in the remote mountain valleys where it is cultivated.  But Emshwiller has seen disturbing evidence that even obscure little oca is being threatened by urbanization and the changes introduced into village life from distant and “developed” countries.

Emshwiller is working with the International Potato Center in Peru to study and maintain the varieties of oca that are being threatened.  It’s not easy.  Because oca reproduces clonally and not by seed, you can’t stick seed samples in a Doomsday vault somewhere.  You have to grow new plants from old plants every year, or the line vanishes.


Artist impression of entrance to Doomsday Vault on a remote island near the North Pole. Gives a whole new meaning to the concept of Santa Claus. Have we been good little girls and boys?)

Emshwiller remains hopeful that oca in at least some of its varieties will not be lost to South America.  She said The International Potato Center has been hosting biodiversity fairs and other projects to encourage people to hang onto oca’s  lumpy, bittersweet possibilities.

Aldo Leopold said, “The first rule of intelligent tinkering is to save all the pieces.”  We have already thrown away so many pieces.  I hope we will save the gnarly little tubers that have been helping to support a tiny population in South American cloud forests for 10,000 years.

2 replies

    • Thanks for commenting, Julio-Cesar. Your market is a lucky one. For those who aren’t familiar with OCA, check out their website here http://www.organicconsumers.org/
      It’s great to learn about more effort being made to spread the bounty of farmers markets.

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