Dam vegetation

A dam on our property in Western Victoria is in the middle of a paddock of pasture that has been continuously grazed by stock for decades. Sheep and cows muddy the edges as they drink, and the water levels fluctuate with the seasons. But several years ago a bigger drinking trough was installed in the paddock and the dairy cows that come and go prefer to drink the fresh clean water from the trough so the dam is largely ignored.

I have largely ignored it as well until one day late in January I was looking through the binoculars, scanning the edges of the dam for ducks or plovers, and I noticed some flowers on the surface. I had no idea what they were and at first suspected it to be a weed. But no. It's a perennial plant called a Swamp Lily Ottelia ovalifolia that likes to grow in still or slowly moving fresh water. It has broad leaves, each with seven veins, that float on the surface of the water. (The juvenile leaves are linear and submerged.) The flowers have three petals and are quite large, up to 5 cm in diameter.

Floating Pondweed (background) and flowering Swamp Lilies

Swamp Lily

Swamp Lily flower

Swamp Lily flower and bud

And I noticed something else flowering on the edge of the dam as well. The leaves are very similar to those of the Swamp Lily but you see in the top photo that they don't float so closely on the surface of the water and the flower is completely different. It's Floating Pondweed Potamogeton tricarinatus. The leaves are thick and leathery and have 16 veins and the flower spike is about 40 mm long.

Floating Pondweed leaves and flowers

So now that I've identified the two plants in the dam as native to the area I'm wondering what this one is. It's a rush growing on the edge of the dam and I didn't take much notice of it because I was looking at the other two. It will have to wait until our next visit.

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