The name of the genus to which the grass-leaved pondweed (Potamogeton gramineus) belongs comes from Greek words meaning ‘river’ and ‘neighbour’, which relates to the habitat this species is found in. The specific part of the scientific name, gramineus, means ‘grass-like’ in Greek and this is due to the physical appearance of this species (2).
The submersed leaves of the aquatic grass-leaved pondweed are different in appearance to those above the surface of the water (2) (3). The leaves growing below the water are green to reddish, have three to nine veins on their surface, pointed tips and grow directly from the main stem of the plant rather than growing on individual stalks (3). The leaves of this plant that float on the surface of the water are smaller than those below the surface (3), and are borne on stalks that grow from the main stem (2) (3). The floating leaves are pale green to brown (4) and have between 11 and 19 veins on the surface (2).
The green-brown flowers of the grass-leaved pondweed are cylindrical in shape (2) and the fruit may be dry or fleshy (5) with straight or slightly curved appendages at the tip that are known as ‘beaks’ (3).The appearance of the grass-leaved pondweed is highly variable depending on the depth of the water in which it has grown (5).
There are three subspecies of the grass-leaved pondweed: Potamogeton gramineus gramineus, Potamogeton gramineus myriophyllus and Potamogeton gramineus maximus. All subspecies of this plant have different-shaped leaves (4).
- Also known as
- variableleaf pondweed, various-leaved pondweed.
Grass-leaved pondweed biology
Very little is known about the biology of the grass-leaved pondweed, although it is known to be a perennial species, living for over two years, and is herbaceous, therefore the aerial parts of the plants die at the end of every growing season (6). The main growth period of this species generally occurs between summer and autumn (4). This plant is thought to reproduce sexually by seed production and dispersal and asexually via rhizomes and tubers (3). The grass-leaved pondweed is known to hybridise with other pondweed species, creating individuals with intermediate physical characteristics (3).
Grass-leaved pondweed range
The range of the grass-leaved pondweed stretches across the Northern Hemisphere (3), encompassing most of Canada and the United States, Greenland and Eurasia (4).
Grass-leaved pondweed habitat
The grass-leaved pondweed is found in ponds, lakes, streams and rivers (4) (6) in shallow and deep water (3). This species inhabits areas with varying water quality, although it is generally not found in acidic or eutrophic water bodies (6). Individuals of this species can be found up to elevations of 3,500 metres (4).
Grass-leaved pondweed status
The grass-leaved pondweed has not yet been assessed by the IUCN.
Grass-leaved pondweed threats
The grass-leaved pondweed has declined in certain areas of its range due to land use changes that have reduced the amount of suitable habitat (6).
Grass-leaved pondweed conservation
There are not currently known to be any conservation measures in place for the grass-leaved pondweed, although it is listed as threatened in Illinois and endangered in Ohio and Pennsylvania in the United States (7).
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- Of asexual reproduction: reproduction that does not involve the formation of sex cells (‘gametes’). In many species, asexual reproduction can occur by existing cells splitting into two, or part of the organism breaking away and developing into a separate individual. Some animals, including vertebrates, can also develop from unfertilised eggs; this process, known as parthenogenesis, gives rise to offspring that are genetically identical to the parent.
- A process in which a water body is enriched with excessive nutrients (such as nitrogen and phosphorus) resulting in the excessive growth of aquatic plants and the depletion of oxygen, creating unfavourable conditions for other organisms, such as fish.
- A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ scientific species name; the second part is the specific name.
- Describes a small, non-woody, seed bearing plant in which all the aerial parts die back at the end of each growing season.
- Cross-breeding between two different species or subspecies.
- A plant that normally lives for more than two years. After an initial period, the plant usually produces flowers once a year.
- An underground, horizontal plant stem that produces roots and shoots.
- A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
- In plants, a thickened stem or root that acts as an underground storage organ. Roots and shoots grow from growth buds, called ‘eyes’, on the surface of the tuber.