Water Hyacinth (Eichhornia crassipes)

Eichhornia crassipes, commonly known as Common Water Hyacinth, is an aquatic plant native to the Amazon basin, and is often considered a highly problematic invasive species outside its native range.

Azolla filiculoides (Water Fern)

Azolla filiculoides (Water Fern) is a species of Azolla, native to warm temperate and tropical regions of the Americas as well as most of the old world including Asia and Australia.

Azolla filiculoides
 image source: http://en.wikipedia.org/wiki/User:Mygaia

It is a floating aquatic fern, with very fast growth, capable of spreading over lake surfaces to give complete coverage of the water in only a few months. Each individual plant is 1-2 cm across, green tinged pink, orange or red at the edges, branching freely, and breaking into smaller sections as it grows. It is not tolerant of cold temperatures, and in temperate regions it largely dies back in winter, surviving by means of submerged buds. Like other species of Azolla, it can fix nitrogen from the air.

Fossil records from as recent as the last interglacials are known from several locations in Europe (Hyde et al. 1978).

Nuphar advena (spatterdock or yellow pond-lily)

Nuphar advena (spatterdock or yellow pond-lily) is a species of Nuphar native throughout the eastern United States, and just into the extreme south of Canada. It is similar to the Eurasian species N. lutea, and is treated as a subspecies of it by some botanists, though differing significantly in genetics.

It is locally naturalized in Britain.

Nuphar advena
 image source: http://flickr.com/photos/8435962@N06

Egeria densa

Egeria densa

Egeria densa (syn. Anacharis densa (Planch.) Vict., Elodea densa (Planch.) Casp.; Large-flowered Waterweed or Brazilian Waterweed) is a species of Egeria native to warm temperate South America in southeastern Brazil, Argentina, and Uruguay.

It is an aquatic plant growing in water up to 4 m deep, with trailings stems to 2 m or more long, producing roots at intervals along the stem. The leaves are produced in whorls of four to eight, 1–4 cm long and 2–5 mm broad, with an acute apex. It is dioecious, with male and female flowers on separate plants; the flowers are 12–20 mm diameter, with three broad, rounded, white petals, 8–10 mm long on male plants, and 6–7 mm long on female plants.

 image source: http://de.wikipedia.org/wiki/Benutzer:ErnstA

Nitella flexilis

Nitella flexilis is a freshwater species of characean algae that is used as a model organism for its large cell size and relative ease of cultivation in the laboratory.


A robust species growing up to a meter long with axes up to 1mm wide. Branches in whorls once or twice divided.

Aponogeton ulvaceus

Aponogeton ulvaceus is a submerged aquatic plant with a small cone shaped, slightly hairy rhizome about 1.18 inches (30mm) in diameter. The leaf blades have a base that tapers gradually, pale green in colour (reddish under intense light), 20+ inches (50+ cm) long and 3 inches (8 cm) broad, with a wavy margin on petioles of an equal length, and in appearance slightly translucent. A single bulb may produce up to forty leaves in good conditions. No floating leaves are formed.

The yellow flowers are produced on an 2(-5) erect spikes.

Aponogeton ulvaceus
 image source: http://commons.wikimedia.org/w/index.php?title=User:Ozhe&action=edit&redlink=1

Echinodorus tenellus

Common names

Pygmy chain sword plant

Echinodorus tenellus
 image source: http://www.flickr.com/photos/clearlydived/


Alisma tenellus Martius; Alisma tenellum; Echinodorus naine; Echinodorus parvulus Engelm.; Echinodorus tenellus var. ecostatus; Echinodorus tenellus (Mart.) Buch. var. latifolius (Seub.) Fassett; Echinodorus tenellus (Mart.) Buch. var. parvulus (Engelm.) Fassett; Helianthium parvulum (Engelm.) Britt.; Helianthium tenellum Britt.; Sagittaria microfolia.