Part 48 Tropaeolaceae - Turneraceae - Ulmaceae
Tropaeolaceae, the nasturtium family, has a single species on the Hawaiian Islands, the common and very familiar garden nasturtium Tropaeolum majus. Hawaiians call this plant pohe haole, or foreign pohe; pohe is Hydrocotyle verticillata, the marsh pennywort, a member of the unrelated family Araliaceae. Tropaeolum majus (see image) has become naturalized on most of the main islands, with the usual exception of Ni`ihau and Kaho`olawe. The plant is admittedly very attractive but it can spread and become a serious pest. Some years ago it got a start in Kipuka Puaulu, known locally as the Bird Park, on the Big Island, and had to be eradicated before it spread beyond control. It is a very common member of the roadside weed community in northwestern Kaua`i where the photograph was taken.
The only member of this genus, which is widespread from Mexico to Argentina, is Turnera ulmifolia, the yellow alder (see image). It is widely naturalized in dry, disturbed habitats on Kaua`i and Moloka`i. We encountered this specimen on the northern coast of Moloka`i.
The elm family, Ulmaceae, have a single representative on the Hawaiian Islands, Trema orientalis (images), known commonly as the gunpowder or charcoal tree. This is a fast growing plant often used in Asia to produce charcoal for gunpowder and fireworks. It is a pioneer plant and can become invasive if allowed to have its way. It is present on all of the main islands with the usual exception of Ni`ihau and Kaho`olawe.
October 11, 2012