Hydrilla, Elodea, Egeria

In soft-water streams and lakes in the Carolinas, Hydrilla doesn't always grow those tiny prickles on the underside of the leaf midrib that give it the textbook rough feel. A few times I've collected what I thought/hoped was native Elodea canadensis (smooth, 3 leaves per whorl) only to have it "turn into" Hydrilla (4-6 leaves per whorl, with tiny prickles visible under magnification, but not by feel). I have yet to find a reliable characteristic to distinguish small 3-whorled Hydrilla from Elodea, especially if I can't get at the roots to check for tubers. Laura or anybody else have ideas?

HYDRILLA:
Be sure to check if you have Hydrilla, I don't know about FL, but it is extremely illegal because it is extremely invasive.

To determine Hydrilla from Elodea or Egeria (which are similar in appearance) simply run a stalk through your hand, wrapped fingers around it kind of, and you will feel the roughness of Hydrilla; the others are smooth.

Umm... carry a hand lens?

My guess is that the Hydrilla you are collecting are bits that come from deeper water where the nodes are spaced farther apart and the whole thing has a more wispy look to it (more like E. canadensis).

I haven't really sat down to look at differences other than the teeth. If you have one, bring a sample to the convention and we can play with it.

Laura

Why is hydrilla "bad" and elodea "good" if they're basically the same plant?

Why is hydrilla "bad" and elodea "good" if they're basically the same plant?

Because basically they aren't the same plant. Hydrilla is listed here as a Federal Noxious Weed. It displaces the similar but native species.

Smothering native plants, clogging dams, hydropower facilities, pumps for cooling tanks (nuclear energy?) is only the beginning. Can't forget about that Hydrilla harbors the nasty blue-green algae (cyanobacteria) that is toxic to birds! The Wilde lab here at UGA is working a lot with this currently. Off topic - my apologies, Gerald.

Smothering native plants, clogging dams, hydropower facilities, pumps for cooling tanks (nuclear energy?) is only the beginning. Can't forget about that Hydrilla harbors the nasty blue-green algae (cyanobacteria) that is toxic to birds! The Wilde lab here at UGA is working a lot with this currently. Off topic - my apologies, Gerald.

Then I think I have my answer as to what I have.
I just got a pretty bad infestation in the tank I'm growing out what I assume is now hydrilla.
Didn't feel any teeth like gerald said either sooo...Horray! I hate Hydrilla and cyanobacteria.

Then I think I have my answer as to what I have.
I just got a pretty bad infestation in the tank I'm growing out what I assume is now hydrilla.
Didn't feel any teeth like gerald said either sooo...Horray! I hate Hydrilla and cyanobacteria.

You can't judge what plant it is based on its growth rate. My elodea densa used to compete with my ceratophyllum for growth speed, and that's saying something (ceratophyllum can easily grow four inches in a day).

You can't judge what plant it is based on its growth rate. My elodea densa used to compete with my ceratophyllum for growth speed, and that's saying something (ceratophyllum can easily grow four inches in a day).

I..what? I was making the classification assumption due to the cyanobacteria infection after the introduction of the Hydrillia, or whatever it is, following what UncleWillie said. I was growing it out to see if the 'teeth' would become more pronounced and ease I.D. I would assume there are other methods for cyano infection, but we'll just blame the plant and call it a day. It's not that important in the tank anyway, the Hydrilla that is.

I..what? I was making the classification assumption due to the cyanobacteria infection after the introduction of the Hydrillia, or whatever it is, following what UncleWillie said. I was growing it out to see if the 'teeth' would become more pronounced and ease I.D. I would assume there are other methods for cyano infection, but we'll just blame the plant and call it a day. It's not that important in the tank anyway, the Hydrilla that is.

I have a bunch of elodea/egeria densa/anacharis if you want to do a comparison, I think i've seen hydrilla but i've never collected it.

I got curious and looked it up. According to http://www.dnr.sc.go...charisalert.pdf , Elodea canadensis has leaves in whorls of 3. Egeria densa has leaves in whorls of 3-4. Hydrilla verticillata has leaves in whorls of 3-8. So cut your plant and examine the cross section. If it's above 4, it has to be hydrilla. If it's 4, it has to be either egeria or hydrilla. And if it's 3 it could be anything, and we try a different way to ID it. There are pictures on the pdf.

I got curious and looked it up. According to http://www.dnr.sc.go...charisalert.pdf , Elodea canadensis has leaves in whorls of 3. Egeria densa has leaves in whorls of 3-4. Hydrilla verticillata has leaves in whorls of 3-8. So cut your plant and examine the cross section. If it's above 4, it has to be hydrilla. If it's 4, it has to be either egeria or hydrilla. And if it's 3 it could be anything, and we try a different way to ID it. There are pictures on the pdf.

In my experience, under good lighting, hydrilla and egeria are likely to develop more of their leaves than just 3. But in the natural environment, if the lighting isn't strong enough, they can develop wispy strands with fewer leaves as they try to elongate to get more light. At this point they can look more like elodea.