(A responsive supply chain)

Hamelia patens*

Rubiaceae

In and near our backyard butterfly garden there are about six firebushes, three of them planted by me in convenient places, and three by birds in weird places.   Birds devour the fruits, produced year-round although in uneven quantities. Hey, being a member of the Coffee Family, maybe they have caffeine. (Just kidding, I think.)

Anyhow, the red and black juxtaposition among the variably aged fruits is one often seen in fruits and seeds of other species that attract birds.   (Think of Precatory Beans, or Nutmeg, or Coal Bean seeds, or ripening blackberries.)

And there is more to the color variation than just advertising.  What’s the point of advertising if you can’t meet demand? The sequence of Firebush fruit ripening is green to cream to pink to murder-scene blood to black.   As UF ecologist Douglas Levey documented in the 80s followed up by others,  when birds (or experimenters) remove the ripe fruits,  the Firebush promptly ripens new ones.  Sort of like when shoppers remove the toilet paper from the shelf in Walmart, the store brings out more (we hope).   No big surprise in the box store,  but a pretty neat supply chain trick for shrubbery. And, in addition to feeding the useful bird seed dispersers, the replenishment of black fruits continues the red-black advertising.

You might wonder, as researchers have, if the responsive ripening is merely that removing older fruits frees up sugar to beef up younger fruits.   That does not seem likely because extra sugar would probably go into the smallest green fruits, but the opposite happens.  When migrating birds gobble up the ripe fruits the plant needs more ripe ones immediately while the migrating birds are still around.  So the accelerated ripening tops off the almost-ripe fruits.   In other words, the nearly ripe fruits are safely in reserve until hungry birds send the signal, “hey, get ripe, we’re here and hungry, it’s crunch time.”

*Not relevant, but to cover all bases I should mention that botanist Thomas Elias,  who studied Hamelia in depth a few decades  ago, pointed out the  that a variety of Firebush (var. glabra) in the nursery trade is not native to Florida, whereas a different variety of the same species (var. patens) is.  Click for a summary.   

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