Broad-leaved Potamogetons with only opaque floating leaves present (or appearing so)

Potamogeton natans Broad-leaved Pondweed

• Flexible lighter coloured stretch of stalk usually present below the leaf, allowing the leaf to sit on the water surface at an angle to the stalk acting like a hinge. Hold the stalk and the leaf will hang down and swing more freely than P. polygonifolius.

• Stipules long, >4 cm, acute/subacute, usually stiff and cloudy translucent, especially when dry.

• Leaves when held up to light with fine hair-like translucent longitudinal veins but cross veins very inconspicuous.

• Leaf stalk > 1 times as long as blade.

• Leaf stalk of even width throughout, with the blade sometimes decurrent onto stalk for a few mm.

• Fruits 3.8-5.0 mm which is larger than most other Potamogetons.

• Long leaf-stalk-like "phyllodes" produced underwater.

• Widespread and in all water types except brackish.

Potamogeton polygonifolius Bog Pondweed

• Leaf stalk of uniform colour to base of leaf, with the stalk running in a straight line into the leaf midrib. If you hold the stalk the leaf blade is more rigidly attached than P. natans.

• Stipules < 6.5 cm, obtuse and sometime hooded, usually floppy and translucent

• Leaves when held to light with network of longitudinal and cross veins similar in colour or darker than the leaf

• Leaf stalk >0.5 times as long as blade (rarely <0.5 in 1-2- unopened leaves)

• Leaf stalk at apex slightly less than 2 x width at base with blade sometimes decurrent onto stalk for a few mm

• Fruits 1.9-2.6 mm

• May produce translucent underwater entire leaves which are stalked and narrowly lanceolate.

• Neutral to acid habitat, in ditches and peatland.

(Potamogeton coloratus Fen Pondweed

• Not recorded in Lanarkshire, Renfrewshire or Dunbartonshire as it is only found in alkaline water.

• Leaf stalk of uniform colour to base of leaf, with the stalk running in a straight line into the leaf midrib.

• Stipules < 6.5 cm, obtuse and translucent.

• Leaves when held to light with network of longitudinal and conspicuous cross-veins similar in colour or darker than the leaf.

• Leaf stalk 0.1-0.5 times as long as blade (rarely >0.5 on underwater leaves in deep water).

• Leaf stalk at apex more than 2 x width at base, with blade decurrent onto stalk for up to 1.5 cm.

• Fruits 1.5-1.9 mm.

• May produce translucent underwater leaves and floating leaves often not fully opaque.)

Notes: P. gramineus, P. alpinus, P. nodosus, P. x nitens and P. x sparganifolius also produce floating leaves and very rarely may lack translucent leaves when stranded on the draw-down zone when water levels have fallen. P. x sparganifolius may superficially appear to lack underwater leaves but these are like the leafstalk-like phyllodes of P. natans but with a narrow strip of translucent tissue along much of their length.

Broad-leaved Potamogetons with some translucent underwater leaves present.

Leaf tip of translucent leaves acute to mucronate

Opposite leaves without stalks

Groenlandia densa Opposite-leaved Pondweed

• Only very old record in Lanarkshire.

• Has rounded often somewhat clasping bases and very finely toothed ends (x10) to the leaves.

Also consider P. x nitens or P. x salicifolius

Translucent leaves without stalks, with tapered (cuneate) bases *

Potamogeton gramineus Various-leaved Pondweed

• Stipules short, to 2.5 cm on main stem, to 1 cm on side branches, often rolled along length into a spike.

• Leaves often have upwardly curved sides but arch downwards lengthways and are delicate.

• Submerged leaves stalkless, but upper leaves may have a stalk as they transition to the floating leaves. They maybe mucronate and have fine denticulate margins (x10). 3-4 lateral veins.

• May have opaque floating leaves with 5-10 lateral veins and conspicuous secondary veins.

• A very variable plant and in a wide range of habitats from middle acidic to alkaline, nutrient poor to moderately nutrient rich. Rare in streams and usually < 1m depth.

Notes also consider P.x angustifloius, P. x salicifolius, P.x sparganifolius.

Translucent leaves stalked

Potamogeton lucens Shining Pondweed

• leaf stalk < 1 cm and leaf base in tapered into it.

• leaves are glossy, translucent, elliptical, with wavy edges and minutely denticulate (x10). They have a prominent pale midrib. The secondary veins tend to slant towards the tip of the leaf.

• stipules 3-8 cm rounded at the top with many veins, two of which are more prominent and form wings.

• neutral to weakly alkaline, mildly nutrient-rich lakes, rivers and canals.

(Potamogeton nodosus Lodden Pondweed

• leaf stalk > 3 cm May have opaque floating leaves  Rare, southern England)

Leaf tip of translucent leaves obtuse to rounded (can be tapered but tip itself is obtuse)

Translucent leaves without stalks, with rounded often somewhat clasping bases

Potamogeton perfoliatus Perfoliate Pondweed

• stipules small and very soon decaying (i.e. usually absent).

• Leaves usually elliptic, wavy edges and minutely denticulate (x10) and clearly clasping the stem and slightly hooded at apex.

• weakly acid to alkaline, mildly nutrient-rich lakes, rivers and canals and weakly brackish water.

Potamogeton praelongus Long-stalked Pondweed

• stipules > 1 cm., persistent, milky translucent especially when dry.

• Leaves oblong-lanceolate undulate entire margins with obtuse hooded tip. Slightly clasping the stem at the base.

• Long stemmed and prefers larger water bodies

Potamogeton crispus Curled Pondweed

• leaves oblong to linear with strongly toothed edges. Rounded to cuneate at base.

• Stipules short and fall off

• Stem flattened and grooved on broad face.

• grows in a wide range of habitats 

Notes consider P.x nitens, P.x salicifolius