Last updated: October 24th, 2024 by Grant Fessler
Overview
Marshes develop on poorly draining to very poorly draining depressions often in floodplains of streams and rivers. These areas are subject to flooding and usually have water above or near the surface for most of the year. In the Quad Cities Region, floodplain marshes along the Mississippi and Rock Rivers are often associated with silt loams, silty clay loams, and clay loams which formed from alluvial deposits and glacial lake plains. Since soils are so wet, it is exceptionally difficult for trees to establish, and thus, marshes are predominantly composed of herbaceous vegetation that can tolerate these conditions. Marsh systems are diverse and dynamic, and the vegetation organizes itself according to water depth and length of flooding. Typical marshes include submergent, emergent and free-floating vegetation. Below are typical native vascular plant associations found in floodplain marshes in the Quad Cities Region.
Related communities: Floodplain Forest
Submergent Marsh:
These species grow completely or mostly submerged in water and are usually found in shallow to deep water. This community typically grades into open water and emergent vegetation.
Submergent marsh vegetation is characterized by: Ceratophyllum demersum, Elodea nuttallii, Nymphaea odorata, Pontederia cordata, Potamogeton spp., Utricularia macrorhiza, and Vallisneria americana.
Emergent Marsh:
A robust emergent marsh dominated by Sagittaria latifolia and Bolboschoenus fluviatilis. 
Sagittaria latifolia in bloom. 
Hibiscus laevis, a common species of floodplain marshes. 
An emergent marsh community characterized by Hibiscus laevis, Cephalanthus occidentalis, Sicyos angulatus, Persicaria coccinea, Sagittaria latifolia, and Leersia oryzoides. 
Emergent marsh vegetation comprised of Leersia oryzoides, Sagittaria latifolia, and Bolboschoenus fluviatilis.
The emergent community is found in soils that are seasonally flooded to wet and comprises vascular plants which grow out of the water. It may grade into submergent, mudflat, and floodplain forest communities.
Emergent marsh vegetation is characterized by: Alisma triviale, Asclepias incarnata, Bolboschoenus fluviatilis, Carex emoryi, Carex laeviconica, Echinochloa muricata, Hibiscus laevis, Iris shrevei, Leersia oryzoides, Penthorum sedoides, Persicaria coccinea, Persicaria lapathifolia, Persicaria pensylvanica, Persicaria punctata, Rumex verticillatus, Sagittaria brevirostra, Sagittaria cuneata, Sagittaria latifolia, Schoenoplectus tabernaemontani, Sium suave, Sparganium eurycarpum, and Typha latifolia.
In particular, the following species usually dominate: Bolboschoenus fluviatilis, Leersia oryzoides, Persicaria coccinea, Sagittaria latifolia, and Typha latifolia. Less common but characteristic marsh species include: Cicuta bulbifera, Lysimachia thyrsiflora, and Persicaria sagittata.
Scattered individuals of floodplain shrub and tree species are usually present. Species include: Acer saccharinum, Amorpha fruticosa, Cephalanthus occidentalis, Cornus obliqua, Fraxinus lanceolata, Salix amygdaloides, Salix interior, and Salix nigra.
Mudflats and Receding Shorelines:
Recently exposed mudflat and rivershore along the Mississippi River. 
A lush carpet of mudflat vegetation and associated shrub thicket dominated by Salix and Cephalanthus occidentalis. 
A gravel bar in the Rock River greening up with annual vegetation. 
Characteristic mudflat association including Eragrostis hypnoides, Ludwigia palustris, Eleocharis sp., and Ammannia robusta. 
Lindernia dubia 
Lindernia dubia blooming on a gravel bar in the ROck River. 
Cyperus subsquarrosus growing on a recently exposed gravel bar. 
Cyperus subsquarrosus 
Ludwigia palustris 
Cyperus squarrosus in bloom. 
Capsules of Ammannia robusta. 
Ammannia robusta
In late summer, water levels typically drop and expose bare soil, also called mudflats. In a matter of weeks, mudflats become lush carpets of vegetation evolved to take advantage of this temporal phenomenon. This community appears on bare, previously flooded silty and mucky soils in marshes as well as on sandy and gravelly substrates along riverbanks. Annuals dominate the association, and Eragrostis hypnoides can be locally dominant and consistently co-occurs with Ammannia robusta and Lindernia dubia. Mudflats may grade into emergent and submergent marsh communities.
Mudflat and receding shoreline vegetation is characterized by: Amaranthus tuberculatus, Ammannia robusta, Bidens cernua, Bidens frondosa, Cyperus squarrosus, Cyperus strigosus, Cyperus odoratus, Cyperus subsquarrosus, Echinochloa muricata, Eclipta prostrata, Eleocharis acicularis, Eleocharis obtusa, Eragrostis hypnoides, Lindernia dubia, Ludwigia palustris americana, Phyla lanceolata, Ranunculus sceleratus, Rotala ramosior, and Xanthium strumarium. Bacopa rotundifolia and Leucospora multifida are uncommon but characteristic species.