| Author | L. | |
| Distribution | Mostly Outer Banks and outer Coastal Plain; scattered records in the lower and central Piedmont, west to Stokes and Davidson counties. A collection from far western Cherokee County may be an introduction.
Que. and MA to MN and SD, south to southern FL and TX. | |
| Abundance | Fairly common to common in the lower Coastal Plain, including coastal islands; close to tidal waters. Away from tidal waters, generally uncommon and quite local, spotty in occurrence west to the central Piedmont. | |
| Habitat | Margins of fresh-tidal rivers, tidal swamp forests, fresh and fresh-tidal marshes, interdune marshes and ponds; old oxbows and brownwater river meanders (Piedmont); openings in swamp forests. This is a strong wetland species, typically in rather undisturbed habitats (for a Rumex). | |
| Phenology | Flowering and fruiting April-July. | |
| Identification | Swamp Dock is robust and typically grows 2-4 feet tall, with lance-shaped leaves to at least 6 inches long. The terminal inflorescence has strongly ascending branches, along which the numerous flowers are grouped in whorls of 10-15. The fruits are small and winged, light yellow green in color. Each flower stalk is 10-15 mm long, vs. 3-8 mm in the very similar Pale Dock (R. altissimus). This distinction can easily be seen without a hand lens; Swamp Dock has drooping or dangling flowers and fruits (as the pedicels are much longer than the flowers and fruits), whereas those in Pale Dock are essentially sessile and appear tight to the branches. In our tidal fresh marshes, this can be a conspicuous plant, with its strap-like leaves and steeple-shaped inflorescence, standing apart from the dominant grasses, sedges, and rushes with their linear leaves. | |
| Taxonomic Comments | None, though Weakley (2018) and a few other references have -- controversially -- pulled R. floridanus from this species.
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| Other Common Name(s) | Water Dock | |
| State Rank | S4 | |
| Global Rank | G5 | |
| State Status | | |
| US Status | | |
| USACE-agcp | FACW link |
| USACE-emp | OBL link |
