I didn't find any dragonfruit (which I've been wanting to try), but they had cherimoyas, jackfruit, different cacti pieces, sugarcane, cassava, weird bananas, all kinds of odd leafy vegetables and squash-like things that were a couple feet across! Faced with a produce section full of things I barely recognized, I thought I should do some homework...
Having made a previous effort to learn the most popular tropical fruits, I spent some time this week catching up on tropical root crops: cassava (a major crop worldwide, available in your supermarket as "yuca root"), yams (a monocot unrelated to the dicotyledonous sweet potato) and taro (which turns out to be an aroid!). All of these are full of poison when raw (which isn't necessarily a bad thing*). They're also described very thinly on the internet (aside from some nice summaries from CGIAR) - but I managed to find some non-Wikipedia citations for the most exotic of these, taro.
Taro (Colocasia esculenta) is in the Arum family, along with a number of similar edible plants, all of which are referred to as "elephant ears" when grown ornamentally. I never paid much attention to this family growing up in the Mid-Atlantic, as I only really knew it for the novelty of jack-in-the-pulpits and skunk cabbage. This family, however, contains lots of famous tropicals: Anthurium, peace lilies, Philodendron, dumb cane, the enormous titan arum and the minuscule duckweed. Many of these species protect themselves by producing needle-like crystals of calcium oxalate - which (in edible species) can be de-activated by cooking or dissolved by acidic ingredients.
Taro is an ancient crop, having been domesticated thousands of years ago in Southeast Asia. Ever since, it's been helping to support small communities across diverse cultures - particularly in times of food insecurity thanks to its reliably high productivity. It's proved especially popular in Southeast Asia and Oceania, where it followed island-hopping humans, adapting to local environments along the way. Before there was rice in Japan, there was taro (known as satoimo, "village/home-root/tuber").** Today it's the 14th most popular staple vegetable crop and is grown across much of the tropics, often cultivated in flooded paddies or in otherwise difficult to use swampy lowlands. Grown primarily for its edible corms (when cooked properly!), this useful plant also produces edible leaves, petioles, stolons and inflorescences, some of which can be preserved and stored for long periods of time by drying or pickling.
Along with calcium oxalate crystals, taro also protects itself with proteases, mucilage and a number of minor toxic chemicals. While not particularly appetizing, they make this crop resistant to many pests and can be mostly removed by proper preparation. People have come up with many different ways to accomplish this (e.g. peeling, baking, boiling, chipping, mashing, fermenting, grating, pickling, leaching, or with chemical additives such as lime juice or tamarind). Many of these treatments were invented independently by different cultures in order to optimally process their favorite varieties into their favorite foods. In Hawaii, for example, the popular food poi is created by peeling and boiling taro corms (to remove acridity), followed by a short fermentation period to manipulate flavor and texture.
As an "orphan crop," taro has been largely ignored by large scale research and breeding operations and its genetic diversity and success remains in the hands of the small communities and peasant farmers who have grown it for generations (and who selected intensely for varieties that performed well in local environments and uses). This selection over generations of migrating and changing human cultures (along with somatic mutation and rare sexual recombination) produced a diverse range of taro varieties with very different phenotypes - a diversity that is now threatened by the adoption of newer high-yielding varieties. Conveniently, this is one crop that's proved amenable to participatory breeding (where professional breeders collaborate with farmers to generate and select phenotypic diversity). Likewise, efforts are being made to conserve and improve the germplasm of this important (but largely subsistence) crop with a collaborative network of national/regional core collections and on-farm specialty variety collections.
I love the way the story of taro ties together deep cultural traditions, modern professional-amateur collaboration and tropical agricultural development. I'll have to find more time to see what other tropical crop stories are out there.
Ramanatha Rao V., Matthews Peter J., Eyzaguirre Pablo B., & Hunter D. editors (2010). The Global Diversity of Taro: Ethnobotany and Conservation Bioversity International
Link to Publication
There're lots of really interesting stories in this pub - especially on the construction of germplasm/breeding operations and strategies (and the unique challenges of working with a vegetatively-propagated root crop), but it's beyond the time I have to write this post!
* I seem to remember some research group embarking on the breeding of a cyanide-free cassava - which was roundly rejected by farmers who preferred tedious processing over a more palatable variety that was a magnet for pests and thieves.
** It's been suggested that the Japanese appreciation of slimy food textures began with taro. On a related note, I was talking to my coworkers today about how Japanese recipes always seem to highly process (cook/ferment/form into patties and slurries) things that Westerners eat fresh (like vegetables) while eating raw things that we always cook (like seafood). A coworker pointed out that this could be due to geography - as they have lots of seashore and little available land to grow things besides rice, while we have lots of land and are (historically) far from the sea
*** Second image from http://www.webquest.hawaii.edu/kahihi/sciencedictionary/G/garden.php