Ceratophyllum demersum vs echinatum vs submersum?

So, it's possible that I have been calling my plant ceratophyllum demersum but it's actually something else. I was doing research on submersum and now I find out there's a species called echinatum and my mind is blown. I hadn't considered the possibility that there might be other ceratophyllums.

Opinions on what this is?
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Where did you get it? It looks like submersum since it's so soft and thin, whereas the C. demersum (no other species grows wild in Iowa according to USDA Plants) I have is stiff, reminiscent of a pine tree. That said, I did not know another species or two besides those was present here in the U.S. I'm willing to bet yours is the tropical kind though, as it's most common in the aquarium trade. This reminds me, there's also more than one native species of Elodea here: the well known canadensis, but also nuttalli. A little more west and you can also find a E. bifoliata, or farther east to find some E. schweinitzii. It's intriguing stuff, I love learning about diversity within a genus I thought I was familiar with. The world has so much variety!

The only thing I could dig up was the auction I originally ordered it for. I learned it was 'grown in the USA' and the vendor is from New York.

I'm seeing Ceratophyllum: demersum, submersum, echinatum, apiculatum, australe, cristatum, floridanum, and llerenae on the USDA plants list. http://plants.usda.gov/java/nameSearch This is going to take me some time to sort through.

C. demersum, submersum, echinatum, and muricatum are the only true species according to the list, the rest are synonyms or subspecies. Grown in the USA? I don't suppose he/she mentioned if it was originally collected from the wild or not?

C. demersum, submersum, echinatum, and muricatum are the only true species according to the list, the rest are synonyms or subspecies. Grown in the USA? I don't suppose he/she mentioned if it was originally collected from the wild or not?

no, that's the only info I had. I think I'm going to go stare at the ID photos until I can tell the species apart by their structures.

Have fun with that I suppose you might have to look at them in flower, though I'm not sure how you would go about doing that. Or perhaps the seeds? Hornwort seeds have a distinct look to them. The stuff I had flowered and went to seed when I ignored pruning for a while and it grew crazy.

im pretty sure that i pulled out some submersum from rhodes pond...
while it has longer leaves, they are softer than demersum.

it looks to me like you have demersum. the echinatum seems to have leaves that branch a lot, and i never saw that in demersum or submersum.

With Hydrilla, water hardness effects the stiffness of the leaves. Hydrilla grown in soft acidic water looks and feels very much like native Elodea, without the characteristic rough feeling that's in every description of Hydrilla I have read. I suspect the texture and leaf length of Ceratophyllum may vary with water chemistry too.

With Hydrilla, water hardness effects the stiffness of the leaves. Hydrilla grown in soft acidic water looks and feels very much like native Elodea, without the characteristic rough feeling that's in every description of Hydrilla I have read. I suspect the texture and leaf length of Ceratophyllum may vary with water chemistry too.

that may be so, but the difference was enough for me to see them when grown in the same tank...

Below is an excerpt from Alan Weakley's Flora of the Southern & Mid-Atlantic region, if it helps. The whole document is a free dowload at the UNC Herbarium website.

C. submersum is not in this key, and the USDA Plants database has no record of it in North America (although introduced, undocumented populations are certainly possible).

107. CERATOPHYLLACEAE S.F. Gray 1821 (Hornwort Family) [in CERATOPHYLLALES]

A peculiar and apparently very primitive family, of a single genus and about 6 species, aquatic herbs, of cosmopolitan

distribution. References: Les in FNA (1997); Les (1985, 1986, 1988a,1988b, 1988c, 1989)=Z; Les in Kubitzki, Rohwer, &

Bittrich (1993). Key adapted from Les.

Ceratophyllum Linnaeus 1753 (Hornwort, Coontail)

A genus of about 6 species, aquatic herbs, of cosmopolitan distribution. References: Les in FNA (1997); Les (1985, 1986,

1988a, 1988b, 1988c, 1989)=Z; Les in Kubitzki, Rohwer, & Bittrich (1993). Key adapted from Les.

Identification notes: Ceratophyllum is sometimes mistaken for other, superficially somewhat similar aquatics, such as Cabomba

(Cabombaceae), Utricularia (Lentibulariaceae), and Myriophyllum (Haloragaceae). Cabomba has the leaves opposite (rather than whorled),

dichotomously divided (like Ceratophyllum), but the divisions lacking the marginal denticles of Ceratophyllum, and on a 1-3 cm long petiole (vs.

sessile or on a petiole 0-2 mm long). Utricularia has the leaves sometimes dichotomously divided, but the divisions are usually irregular, the

leaves are alternate (in most species), and bladder traps are present. Myriophyllum has the leaves pectinately rather than dichotomously divided.

1A Largest leaves forking 1-2× (count branching-nodes from the base of the leaf to the tip of the most-forked division); leaves coarse-textured,

stiff, the marginal denticles usually strongly raised on a broad base of green tissue; achene margin wingless, with 2 basal spines or tubercles

(these rarely absent), otherwise entire (lacking marginal spines) ........................................................................................................ C. demersum

1B Largest leaves forking 3-4× (count branching nodes from the base of the leaf to the tip of the most-forked division); leaves fine-textured,

flaccid, the marginal denticles not raised on a broad base of green tissue, sometimes obscure or obsolete; achene margin winged, with 2-20

lateral spines 0.1-6.5 mm long (occasionally spineless), with 2 basal spines (these rarely absent). ..... 2

2A Achene body (excluding the spines) 3-4.5 mm long; first leaves of the plumule simple; [Coastal Plain, NC southward] ............... C. australe

2B Achene body (excluding the spines) 4.5-6 mm long; first leaves of the plumule forked; [widespread] ..................................... C. echinatum

=================================================================================

Ceratophyllum australe Grisebach. Cp (GA, NC): ponds, pools, slow-moving streams; rare (NC Watch List). May-

September. Se. NC south to s. FL and panhandle FL, and in the West Indies; also in s. Mexico, Central America, n. South

America, with apparent disjunctions in c. South America and the Galapagos Islands. Les treats this taxon as a subspecies of the

Old World C. muricatum. Because of their allopatric distribution on separate continents and relative morphological

distinctiveness (as shown by Les), I prefer to recognize them at the species level. [= Ceratophyllum muricatum Chamisso ssp. australe

(Grisebach) Les – FNA, K, Z; < C. muricatum Chamisso – GW (also see C. echinatum)]

Ceratophyllum demersum Linnaeus, Coontail. Cp (DE, GA, NC, SC, VA), Mt (GA, VA, WV), Pd (DE, VA): ponds,

pools, slow-moving streams; common (uncommon in GA, NC, SC, VA, and WV). May-September. Newfoundland west to AK,

south to s. FL, TX, CA, and south through the West Indies and Central America to South America. [= RAB, C, F, FNA, G, GW, K,

W, S, Z]

Ceratophyllum echinatum A. Gray in Torrey & A. Gray. Cp (DE, NC, SC, VA), Mt (GA, VA, WV), Pd (VA): ponds,

pools, slow-moving streams; uncommon (rare in WV). May-September. Newfoundland west to Ontario and n. MN, south to c.

peninsular FL and e. TX; also in British Columbia, WA, and OR. [= RAB, C, F, FNA, G, K, S, Z; < C. muricatum Chamisso – GW

(also see C. australe); = C. submersum Linnaeus var. echinatum (A. Gray) Wilmot-Dear]

Thank you, that is very helpful. I will compare it to my plants