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Sure, you grow mangoes, but are they blue?

What is the mysterious blue mango?

Most of us are aware of the multitude of mango varieties, even available at your average supermarket. “Cogshall,” “Champagne,” “Angie,” “Haden” are names we may have seen. Try “Fairchild” if you haven’t already — it’s wonderful. But not to worry if you don’t know all the mango varieties, there are only about 600.

For centuries, maybe millennia, mangoes have been cultivated by humans to encourage the qualities we value: less fiber, greater and sweeter flesh, smaller seed, and in more recent times, longer shelf life so we can ship mangoes to our friends up north and have them last.

Most of the varieties we have now fall under the same species: Mangifera indica, but there are also about 70 other Mangifera species. You might just gloss over one of them, say, Mangifera casturi, thinking, “It’s just another mango.”

But then, a couple of years back, I read these words: The blue mango!

A blue mango? It just sounds exotic, like a black pearl, or salted caramel; it’s unexpected. And it’s a different species: the Mangifera casturi. There are even varieties of the blue mango.

And it gets better because it’s quite edible, delicious even. Fairchild’s curator of Tropical Fruit, Noris Ledesma, indicates the fruit is juicy, sweet, with a flavor resembling passion fruit and lychee. And the fruit is blue! Or nearly so. Actually a purple-blue with a naturally waxy coating that makes the skin appear a bit bluer, contrasting nicely with the pumpkin-orange flesh.

The blue mango, also called “Kastoree,” is a rare one indeed. It’s native, and probably endemic, to the south Kalimantan region of Indonesia, which is the Indonesian part of the island of Borneo. Sadly, it’s also included on the International Union for Conservation of Nature’s Red List as “extinct in the wild.”

Fairchild’s curator of tropical fruit, Noris Ledesma, with a fresh crop of blue mangoes. Fairchild Tropical Botanic Garden

The Mangifera casturi, among others, is grown at the Fairchild Farm in Homestead, Florida, as part of our living collection. The genes of this valuable tree have been used to create new hybrids. Ledesma is working on a breeding program, and hundreds of new trees are the progeny now under evaluation. She is looking for the perfect mango for a new generation — mangoes resistant to diseases that can be grown free of heavy chemical products, but are also delicious and nutritious.

Blue mango’s new foliage is bright red, like that of so many tropical plants (an interesting story in its own right), always eye-catching against the deep green, strappy, classically tropical foliage of the mango. It’s known to be resistant to anthracnose and loves our wet subtropical climate. The fruit may be small compared to other mangoes, but hey, it’s blue!

The blue mango can be your ideal fruit tree: an ornamental tree that produces delicious, attractive mangoes. And growing one (or more) makes you part of its ex-situ conservation — that is, growing it away from its natural habitat.

This species and many other mango tree varieties will be available at Fairchild’s Mango Festival, July 13 and 14. See more information at fairchildgarden.org/mango.

Kenneth Setzer is writer and editor at Fairchild Tropical Botanic Garden.