Last few days I’ve been exploring mostly native plants expanding through the mean ecological filter into urban habitats.   Not many country cousins succeed in town.

Out of many challenges (and opportunities)  to native urban expanders are “urban heat islands.”   A cool park beats hot times in the city.   That matters to plants and critters.   It also complicates assessments of climate change.   And you know what heat islands are hotter than hell?  Rocky railroad beds.    They can be more or less 40 degrees F hotter than surrounding areas on hot sunny days,  worse than a Publix parking lot. Not only toasty, but also stones instead of soil,  drained dry,  shadeless, stinky trains polluting past, and occasional herbicides.  No wonder almost nothing grows there.   I was hot-footin’ around the tracks yesterday marevelling at railroad rock dwellers.  There you find Euphorbia lasiocarpa (aka Chamaecyse lasiocarpa), native mostly to Mexico.

Try to look it up in the 1971 classic “Flora of Tropical Florida.”   Not in the book, because in 1971 it was grabbing a Florida toehold south of Miami, however it may have arrived.  And look where it was found first….a RR track, foreshadowing the next 20 years.  This is a species whose northward (and eventually east-west) expansion featured train tracks.  Gathering data from several museums, the earliest 15 records of the species in Florida are shown in the timeline below.

An observer might say, “trains are natural seed transporters,  expanding species distributions.” Sure, but I suspect a minor factor for this species.   An observer might say, “global warming could help a tropical species migrate northward/.”   Okay, but the blazing hot RR track bed is vastly hotter than whatever global warming is in play.

Euphorbia lasiocarpa appears to be at heart adapted to very hot, very dry, very rocky, very unshaded Mexican deserts.    I think the main reason I found it yesterday workin’ on the railroad is that for E. lasiocarpa, “the railroad bed is a little slice of home.”  That unique habitat IMHO extends the Euphorbia’s happy place into Florida where btw it has almost no competitors.

Grass site: www.floridagrassesandsedges.net

John Bradford links: https://tcbradford.wordpress.com/