Iva imbricata, I. frutescens and additional species
A class trip to Blowing Rocks Preserve today on Jupiter Island reminded me that sometimes broad plant groups are collectively interesting—we live in a plant world of genera and families, not just individual species. At Blowing Rocks separated by a couple hundred yards are two representatives of the nine-species genus Iva, which is an odd little bunch in the Aster Family.
Locally the dominant beach plant is Marsh Elder, Iva imbricata. You can’t miss it. On most local beaches it comprises 90% of the vegetation in great green perennial patches on the beach just above the waves and just below (or on) the dunes. The leaves are succulent, mostly opposite, slightly toothy, and fragrant when crushed. The fragrance perhaps accounts for the name Iva in reference to a mint Ajuga iva, although the paper trail on this notion goes cold fast. You scarcely see flowers, because the Iva flower heads are greenish and inconspicuous like those of its relative Ragweed.
I’m always fascinated with the adaptations of beach species. How can they establish and survive on hot, windblown, stormy, abrasive, shifting salty sand? A relevant adaptation of Iva imbricata is the ability of its seeds to sprout anchored far deeper in the sand than typical seed-sprouting depths. The seedlings burrow up from subterrranean safety below the maritime perils to break through to the sunny surface like little skyscrapers drilled basally into the bedrock.
Walk 200 yards to the lee side of Jupiter Island to protected salt flat and there’s a different Iva. Iva frutescens is taller, woody, toothier-margined, and less succulent. Books call it Bigleaf Sumpweed, although I’ve never heard that silly handle in conversation. Other authors call this species Jesuit’s Bark, a name applied more to quinine used to quell fevers and as an antimalarial and promoted by Jesuit missionaries. Applying the name Jesuit’s Bark for Iva frutescens may refer to historical applications against fevers, although few data are handy. Iva species do contain phytochemicals vaguely compatible with such benefits.
There are other Ivas in Florida, including two local annual species Iva angustifolia (outer bracts on flower head fused) and Iva microcephala (outer bracts separate, the clusters < 2 mm long).
Iva annua, is arguably the most interesting species. It ranges across much of eastern North America, including northern Florida. I recall it fondly from living in St. Louis across the Mississippi from the ancient Native American center known as Cahokia. CLICK
Cahokia dates back to the transitional era when maize and beans gained prominence as Native American staples very roughly speaking a little less than a thousand years ago. What grains were important in the pre-maize era? Among them were the “seeds” (achenes) of Iva annua. Now here is the good part: archaeological remains going back some 5000 years show Iva to have been an early staple. Even more remarkable, there were large-seeded “improved” cultivars of Iva annua by 2000 BC in caves, kitchens, and storage for planting. In short, ancient horticulturists developed it as a domesticated crop named by modern botanists Iva annua var. macrocarpa. As a young botanist not long ago I enjoyed searching the wild Iva populations around Cahokia for the macrocarpous strains persisting into modern times. Found some large ones but nothing convincingly “improved and persistent.” The large-seeded strains are presently regarded as extinct, having been elbowed aside by corn around the year 1200. Iva seeds are easy to harvest, are produced abundantly, are easy to prepare, and are nutritious high in nutritious oils. Once so important, now so forgotten. That seems worth knowing.
[Readers interested in ancient large-fruited Iva will enjoy this detailed illustrated account CLICK.]