Spotted pondweed  (Potamogeton pulcher)

The spotted pondweed has not yet been assessed by the IUCN.

A distinctive aquatic plant, the spotted pondweed (Potamogeton pulcher) is, as its common name suggests, characterised by many conspicuous spots, which are scattered on the stems and on some of the leaves (2) (3). This species has both submerged leaves, which remain below the water, and floating leaves, which mass together on the surface (4).

The submerged leaves of the spotted pondweed are usually arranged alternately along the stem, and are narrow and lance-shaped, with wavy margins. These leaves are typically dark green, with a pair of smaller light to dark brown leaves, called stipules, at the base (2) (3) (5) (6). In comparison, the floating leaves of the spotted pondweed are usually light to dark green, oval-shaped and slightly indented at the base, with long black- or purple-spotted leaf stalks (2) (3) (5) (6) (7).

The inflorescences of the spotted pondweed are produced in dense spikes above the water, and each contains many small, inconspicuous flowers. The individual flowers have four small, greenish petals (2) (6) (7). The fruit of this species is olive to dark green or brown, rounded or oval-shaped, and has three prominent ridges on the outer surface (3) (4) (6) (8).

Found only in North America, the spotted pondweed occurs from Nova Scotia In Canada, south to Florida and Alabama, and west to Minnesota, Missouri, Ohio and Texas in the United States (2) (7) (8).  

The spotted pondweed inhabits the shallow, peaty or muddy waters of stagnant or slow-flowing streams, as well as swamps, ponds and lakes (2) (3) (5) (9).

Very little information is available on the biology of the spotted pondweed. This species flowers between June and September, with fruiting occurring around early August or September (2) (3) (9).

The spotted pondweed is likely to be threatened by the degradation of its habitat, as well as by invasive plant species which compete with the spotted pondweed for space and resources (2) (7).

Agricultural run-off and flooding may also affect this species (7).

There are currently no specific conservation measures in place for the spotted pondweed. Recommended conservation actions for this species include protecting its wetland habitat, maintaining water quality and removing invasive species (2) (5).

Creating buffers to protect the spotted pondweed from run-off and flooding may also benefit this species’ populations (7).

Find out more about the spotted pondweed:

• Flora of North America - Spotted pondweed:
  http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=222000301
• Pennsylvania Natural Heritage Program - Spotted pondweed:
  http://www.naturalheritage.state.pa.us/factsheets/15786.pdf