A weed is “a wild plant growing where it is not wanted and in competition with cultivated plants.” Nasturtium is my favorite weed, of the many growing in golden gate park. Its gray-green, disk-shaped leaves and bright orange-red-yellow flowers are undeniably beautiful, and I love how it brightens the ground under the trees in many places in the park. But it grows so rampantly that you can practically watch it smothering everything in its path. I’m reminded of this George Price cartoon that I cut out of the New Yorker many years ago:
Originally from South America, the plants that we commonly refer to as nasturtium actually belong to the genus Trapaeolum (confusingly, the genus Nasturtium is claimed by watercress). There are about 80 species of Trapaeolum and they have the family Trapaeolaceae all to themselves. The species we know so well, the one that has happily naturalized in the U.S., is Trapaeolum magus (Garden nasturtium). It’s originally from the Andes, ranging from Bolivia to Columbia. Carl Linnaeus named this genus Tropaeolum reportedly because the plants reminded him of an ancient Roman custom. After winning a battle, victorious Romans used to set up a trophy pole called a tropaeum and the armour and weapons of the vanquished foe were hung on this pole. Linneaus thought the round nasturtium leaves resembled shields and the flowers, blood-stained helmets. Not a pretty story to attach to such a lovely plant!
A prettier story has to do with the phenomenon of “flashing flowers” associated with nasturtium and discovered by Linnaeus’ daughter Elizabeth. At dusk the small orange flowers sometimes appear to “flash” like tiny lights. It’s not an electrical phenomenon, but an optical illusion in the eye caused by the contrast between the brilliant orange flowers and the deep green of the surrounding foliage. Perhaps related to the green flash that we sometimes see when a bright, orange sun sinks into the sea at sunset?
You have to wonder if someone planted the first nasturtium in Golden Gate Park (could it have been introduced by John McLaren)? Or maybe it just crept in from the Richmond or the Sunset all by itself?