Two Leaf Nightshade (Twin Leaf Solanum)
Solanum diphyllum (FL Exotic Pest Pant Council Cat. II invasive exotic)
Today John and George enjoyed the mangrove swamp at Peck’s Lake near Hobe Sound, a short boardwalk long on biodiversity, including wasps. We had one of those wasp experiences I sorta like—wasps can be our pals. (Stockholm Syndrome.) We somehow riled up the hive, and 133 (I counted) wasps stormed out with gusto and buzzed our heads in a friendly but earnest warning. We took the hint with equal gusto, and nobody got hurt.
As I arrived at the parking lot, John was already photographing the plant of the day…Two Leaf Nightshade, a member of the genus Solanum, with several additional species in Florida, including spuds. With odd mismatched leaf pairs and highway-worker-vest orange fruits in pretty clusters, Solanum diphyllum gathers a lot of “likes” on its Facebook page. You could spot those clustered little oranges from a helicopter.
The species is native to Mexico and Central America, and like a good weed (and as a garden species) it is scattered elsewhere in the warm climate world, maybe with a helping hand from Global Warming and gardeners in addition to wild creatures. Today’s invasive exotic decorates the shores of the Intracoastal in Hobe Sound and likewise decorates the shores of the Nile in Egypt, where it fascinated Egyptian biologist Fatma Hamada of the South Valley University as much as it fascinates us. Hamada’s 2013 doctoral dissertation is a monograph on Solanum diphyllum, looking into everything from its beautiful internal anatomy to its cytotoxicity against human cancer cell lines. (so, no, those fruits are not for us to eat).
One of her findings was particularly intriguing. Many plants of arid or salty places protect themselves from drought and salinity by accumulating extra dissolved materials in their tissues. This is true of our Solanum, and here’s the good part: adjustably. Apparently, and in need for more research, the plant build ups anti-drying compounds when dry, and later secretes the stuff from the leaves when dry times abate. Maybe. Another “maybe” is what seem to be patches of natural “sunblock” embedded in the leaf surface. This little weed has some stuff goin’ on! Now back to those fruits oranger than an orange. Univ. of Miami bat expert Dr. Theodore Fleming described (citing earlier work in South American tropical forest) bird-dispersed fruits to be mostly white, black, red, blue, or purple in contrast with mammal-dispersed fruits predominantly orange, yellow, brown or green. (Please no e-mails: These are broad perceived trends—with overlaps and exceptions.)
So is Solanum diphyllum mainly a mammal berry? Probably, although its dispersal in Florida with almost no fruit-eating bats implicates helpful birds and maybe a quadruped or two. Research in the shrub’s native Mexico proves fruit eating bats to carry the seeds, not necessarily to the exclusion of birds or others of course. Quibblers may raise a hand, and say, “bats are blind as a bat, so ixnay on the orange uit-frays.” But recent research reveals increasingly sophisticated vision in bats, including living color. Here is a quote (2001) from bat biologists Jorge Ortega and Ivan Castro-Arvellano on the Jamaican Fruit Bat widespread in the native haunts of the Two Leaf Nightshade: “A. jamaicensis uses vision and olfaction to ﬁnd fruits with brilliant colors and strong odors.” By the way, bats don’t like getting tangled in twigs at night. Note how the fruit clusters are presented for EZ access. Now back to Egypt, where as we already know, the Nightshade grows up and down the Nile. Guess what was first discovered at the Great Pyramid of Giza, and flutters nocturnally up and down the Nile (and far beyond). The Egyptian Fruit Bat. Could it be that the corresponding Nile distributions of the Solanum and the bat are mere coincidence? A connection might seem tempting to contemplate if Egyptian Fruit Bats go for orange-colored fruits. Who knows?