Colombian Waxweed is a Seed Trebouchet (maybe)

This article has a lot analogies.

Cuphea carthagenensis

(Cuphea comes from Greek for curved, noting the bent flower base. Cartagena, Colombia, is the site of the original specimen.)

Lythraceae, the Crape Myrtle Family

A running theme in my botanical life is, hey, no need for exotic locales to see the best of botany, the back yard ain’t bad.   The plants we tromp while looking for something fancy are often overlooked treats, like shy classmates.  Nobody told Mother Nature to put all the good evolution in tourist brochure locales.   As an example, in wet disturbed areas across much of the Southeastern U.S. and far southward is a pretty little plant you might call a wildflower, or a weed, or “Colombian Waxweed.” Books will state it is not native to Florida, but I never trust such designations with widespread self-fertile masters of dispersal having unknown histories.  When and how it got to Florida from tropical American latitudes is anybody’s guess.

Colombian Waxweed by John Bradford.

Gardeners know the genus Cuphea from such beauties as bat-faced cuphea, candy-corn, cigarplant, and Mexican-heather.   They are pretty, including Cuphea carthagenensis in a modest sort of way.

The long sticky hairs on Cupheas are so graspy-claspy they could remind an observer of the tentacles on carnivorous sundew.  Here is an excerpt from Popular Science Monthly 1904:

Look closely at the photo below of a partial flower touched by a steel needle.  The hairs grabbed and hugged the shaft, conforming instantly to its shape.   Those are some serious “tentacles,” marauding ants beware!

Cuphea flower tube with clasping hairs hugging needle shaft. They grabbed the needle instantly upon touching it.

A second point of human-Cuphea contact is the oil from its seeds garnering attention relative to human dietary health, possibly as oil crops.   The main function of seed oils is as compact high-energy nutrition for the embryo.   In a wetland weed, the oils might additionally resist water damage.

Cuphea carthagenensis has one of the weirdest seed dispersal systems I’ve ever seen.  The “placenta” is the structure inside a fruit where the seeds are attached.    Repeat, inside the fruit.

In today’s species the world’s wackiest placenta thickens, lengthens, and bends upwards ripping open the horizontal flower, busting through the top off the fruit and opening the overlying flower tube.     Think of Dracula sitting up in his coffin, tearing through his shroud (the fruit) and popping the top off the coffin (the horizontal flower tube).

The open flower tube is pointing toward us at the bottom of the photo.   The big pinkish placenta has risen, opening the top of the flower tube.  Six seeds are visible on the placenta.

This leaves a very odd “fruit” looking like a bent shovel, the shovel handle (Dracula) being the placenta, and the toothed shovel blade being the remains of the torn flower tube. Upon rising, the enlarged placenta has seeds on it, dispersing to leave the placenta bare.  The shovel blade is held. nearly horizontal.  The placenta leans back. The unit is hinged to the main stem by a short stalk attached near the angle where the blade meets the handle

Open flower tube (shovel blade) to the left.  Placenta (shovel handle) pink on the right.   Seeds removed.  The hinge is behind the blade-handle junction.

The exposed placenta passes through a pinkish phase.  Why?  Could the color attract creatures involved in dispersing the seeds?   Birds?  Possible, but the shovel units are tiny, and birds just don’t ring likely.  Insects?   Possible, but there is no apparent reward, I’ve never seen any,  the  seeds are not particularly sticky, and the big seeds would be a massive burden on a bee, although an insect visitor coud shake them loose if not cart them off   Again, doesn’t strike me as likely.   Rather, I suspect the colorful placentas enhance the overall attractive display of the entire plant, helping to draw distant pollinators, who once nearby divert to the actual flowers.    Room here for speculation and research!

More abundant than bees, more reliable, and vastly more powerful is the driving rain.   A  raindrop has punch, and the open flower tube shovel blade is sized and positioned for raindrop bombing.

A raindrop smacks the blade downward, popping the hinged placenta up to catapault the seeds.  It makes sense for a plant inhabiting rain-puddle habitats to launch seeds during the deluge.  The seeds go when and where the rainwater goes.

Why is the blade toothed?  Maybe to help capture raindrop impact, yet to also allow drainage.