Sunday, December 20, 2009

Wetland Plant of the Week #38

Iva frutescens “Marsh Elder”

Marsh elder is a perennial, multi-branching shrub that is native to the coastal regions of the southeast United States. It can typically be found inhabiting the ecotones surrounding saltwater and brackish marshes, as well as in the wetland transitional zones associated with the coasts of the Atlantic Ocean and Gulf of Mexico. Though an Obligate species, Iva frutescens has a reduced tolerance for long periods of inundation; this is why it’s found in ecotone areas as opposed to more marsh-centralized localities.

The succulent lanceolate leaves of Iva frutescens maintain a dull green color year around and exhibit an opposite arrangement. The margins of the leaves often display a serrate edge and/or have few sporadically placed teeth. The plant’s green flowers can be found clustered on panicles and appear as a ‘drooping head.’ The fruiting bodies of Iva frutescens exists as oval shaped, dark brown achenes.

The morphological characters displayed by the marsh elder’s achenes demonstrate adaptation to an aquatically driven mechanism of dispersal. The achenes are only about 2mm in length and have a very smooth outer covering; this makes them ideally suited for transport via water. Known as hydrochory, water facilitated seed transport is a strategy that is implemented by a large number of coastally located plant species. In regards to the lineage of Iva frutescens specifically, proximity to tidally influenced waters has selected achenes with a tolerance for saltwater and a proven ability to stay afloat while in a non-dormant condition. In fact, research published just this year has shown that the achenes of Iva frutescens can stay afloat for more than 67 days – that’s pretty impressive. These physiological adaptations have paid large dividends for the marsh elder, as they can be found in abundance from the Gulf Coast of Texas northward along the US shoreline to Canada.

Elsey-Quirk, T., Middleton, B., & Proffitt, C. (2009). Seed flotation and germination of salt marsh plants Aquatic Botany, 91 (1), 40-46 DOI: 10.1016/j.aquabot.2009.02.001

1 comment:

  1. Does it have a peppery aromatic odor when in flower?