Helanthium tenellum
| Echinodorus tenellus | |
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| Species: | E. tenellus
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| Binomial name | |
| Echinodorus tenellus (Martius)Buchenau in Abh. Nat. Ver. Bremen 2:21, 1869
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In Rataj's taxonomy E. tenellus is in Section Tenelli, Subgenus Helianthium
Synonyms
Alisma tenellus Martius
Description
Leaves narrowly elliptical or lanceolate, sometimes the blade is scarecely distinguishable from the petiole, another time the petiole 10 - 15 x as long as the blade; blade usually 1 - 4 x 0.2 - 1 cm; at the tip pointed, base decurrent to the petiole with 1 - 3 veins.
Stem thin, erect, often curved and radicans, 3 - 20 cm long. In small plants the stem ends in a single infloresence (umbel or coil), in larger plants the infloresence is racemose, composed of 2 whorls placed one above the other. Bracts free, in the first whorl 2 - 6 mm long, pedicels 1 - 3.5 cm long. Sepals 3 mm long, membraneous, usually with 5 fine ribs, during ripening the sepals enlarge and reach a length of up to 6 mm and fully cover the aggregate fruit. Stamens 6 - 9, about 1 mm long, anthers 0.25 x 2.25 mm lomg, 3 x shorter than the filaments; number of pistils 16 - 18. Achenes compressed, in apical part arched; (0.9) - 1.1 - (1.3) mm long, black, with 3 lateral ribs. Basis of stylar beak placed under the level of the tip of nutlet, stylar beak 0.1 - 0.3 mm long.
A very variable species according to its geography and environmental conditions.
Distribution
USA to Southern Brazil. Probably the widest distributed of all the Echinodorus, with the most northern range.
There may be several different races, which have at times been given separate taxonomic rank.
It is only rarely found in running water. Normally it is found in wet sand on the shores of pools or in inundated zones of rivers.
Cultivation
Easy to grow. In good light and substrate it can forms mats of plants at the front of the aquarium. It can stand a wide range of temperatures and water conditions if acclimatised.
It will bloom readily in emerse conditions, all year round.