This morning was a time to help John photodocument the aftereffects of fires in Jonathan Dickinson State Park, although charred boonies aren’t all that aesthetic. Scattered around the park are yellow flowery Rattleboxes. Rattleboxes are species of Crotalaria; Rattlesnakes are in part species of Crotalus. What do rattleboxes and rattlesnakes have in common? Beyond the rattle…poison. Showy Rattlebox, C. spectabilis, has killed horses, sometimes after a prolonged delay. Researchers apply the toxin deliberately to suppress an animal’s blood pressure.
But don’t they eat Rattlebox seeds around the world? Yes, but…There are hundreds of species of Crotalaria of unequal nastiness. Being on the menu is no guarantee of complete safety, as not every culture has a long life expectancy, and diet-related illnesses may be cryptic. (Rattleboxed horses sometimes die in the possession of their next owner.) Here’s the obvious thing: do not eat wild plants. Read about them in Treasure Coast Natives, take beautiful photos, and then buy veggies properly.
Showy Rattlebox is abundant locally, with pizzazz yellow blossoms an inch across. It differs from most local relatives by having simple (vs. compound) leaves. Such a showboat might be assumed to have come from its native tropical Asia as a garden flower, but no. The Florida arrival is more interesting, so read on:
The superstar plant introducer in earlier Florida—and there were many—was David Fairchild, immortalized at Fairchild Gardens in Coral Gables. Fairchild was not a mere plant introducer on steroids but equally a champion “social networker.” His friends, associates, and patrons included the rich, influential, and famous of that era, including notables in science and industry: Henry Flagler, Charles Deering of International Harvester (his brother built Vizcaya), Glenn Curtiss of the Curtiss Aeroplane and Motor Company, Orville Wright, Thomas Edison, and you get the idea. Fairchild’s father-in-law was Alexander Graham Bell. Accounts vary, but Fairchild was directly or indirectly responsible for the introduction of a couple hundred thousand exotic species, crops, varieties, and cultivars of plants.
A tree Fairchild brung from China and distributed in the U.S. 1905-1907 was Tung Oil (Aleurites fordii), then valuable in products from printing ink to ammunition. In the early 20th Century Tung supported 400 growers in and near Alachua County, but then it fell into disgrace as a Category II invasive exotic. Times change.
This all leads back to Crotalaria spectabilis. Tung farms grew predominantly on poor sandy soils left denuded from pine deforestation. The system needed enrichment, and Fairchild introduced Showy Rattlebox in the U.S. around 1914 as a sand-loving, heat-tolerant, nitrogen-fixing legume to goose up the Tung. And as an added benefit, Fairchild suggested Showy Rattlebox to deter nematodes, especially among papayas. He apparently was not fully aware of the dangerous livestock toxicity. As with Tung, Showy Rattlebox slipped from celebrity to invasive weed and veterinary menace.
Farmers could not afford commercial fertilizer during The Great Depression. Growing Crotalaria for nitrogen fixation and as green manure was a comparatively cheap alternative. One agricultural agent reported purchase of over 20,000 pounds of Crotalaria seed (C. spectabilis and C. pallida) in and near Orange County during 1931. (Crotalaria pallida is another showy introduced Crotalaria, called Smooth Rattlebox, easily distinguished from C. spectabilis by having three-parted leaves.)
The native Ornate Bella Moth is a Crotalaria specialist feeding naturally on indigenous Crotalaria species. Due to dietary and ecological expansion, the moth may be a natural biocontrol for the invasive exotic crotalarias, damaging them with gusto while hopefully remaining in better ecological balance with the native species. There are four native Crotalaria species in Florida, and about 10 invasives. The moth will be busy for some time, as the seeds can survive 60 years in the soil.
Let’s close with one of the native species, common in JD Park, Crotalaria rotundifolia, better known as Rabbit Bells. It is just a lil’ rattler, with simple leaves, on sunny sandy soils. This variable and vaguely defined species makes big poofy inflated pods. Why should this or any plant make fruits resembling dirigibles? Simplistic speculations are possible and not mutually exclusive: for flotation, for temperature insulation, for padding, for isolating seeds from pests and parasites (with perhaps the gas within inhospitable to tiny varmints), or for containing vaporized hormones. Botanists have discerned another more subtle explanation for inflated pods in other plants. Seeds respire and give off carbon dioxide. Carbon dioxide is the main input into photosynthesis. So why waste it? In poofy pods the internal air space seems to be a carbon dioxide tank, capturing the “waste” carbon dioxide coming out of maturing seeds and feeding it to the inner pod wall to photosynthesize. Perhaps out in the bright sun those translucent pods can use light on their otherwise passive inner surfaces, and make the seeds pay their own way with a CO2 toll for the zeppelin ride.