# Acmella repens?



## davemonkey

If you conduct an internet search for _Acmella repens_ you'll find a few, very few, photos of the plant along with a synonym (_Spilanthes americana_) and probably an older species name (_A. oppositifolia_). In those photos, the flower sits atop a long petiole (at least compared to what I have been calling _Acmella repens_ ) and the flower is quite different compared to some photos.

So, I'd like to know if what I have is the same species. Every specimen I've seen looks like this (pictured below), from Chambers County to San Marcos (Southeast to Middle Texas).

In the 2 habit photos, one was taken in a shady location, the other in full sun and in a drier soil. The plant in the drier soil is much rougher to the touch and the leaves are smaller...which makes sense to me. The plant is hirsute, the hairs short and fine giving a rough texture to the stems and leaves.


----------



## THHNguyen

It looks similar to it. Why don't you try some in your tank? BTW you're so lucky to live near such cool plants!


----------



## ukamikazu

Funny you bring this up. I thought Acmella oppositifolia (Lam.) R.K. Jansen var. repens (Walter) R.K. Jansen 1984 was the current name. I only happen to possess this information after doing an enormous of reading about it today because I was getting ready to go on a collecting mission. Or that is what TROPICOS and the USDA have led me to believe. I haven't checked the RHS/Kew Gardens databases yet.

As far as a positive ID, try this, http://www.missouriplants.com/Yellowopp/Acmella_oppositifolia_page.html.


----------



## HeyPK

We have a similar plant in Central Mississippi. In our variety the disc of the composite flower is much larger and dome-shaped.


----------



## Cavan Allen

ukamikazu said:


> Funny you bring this up. I thought Acmella oppositifolia (Lam.) R.K. Jansen var. repens (Walter) R.K. Jansen 1984 was the current name. I only happen to possess this information after doing an enormous of reading about it today because I was getting ready to go on a collecting mission. Or that is what TROPICOS and the USDA have led me to believe. I haven't checked the RHS/Kew Gardens databases yet.
> 
> As far as a positive ID, try this, http://www.missouriplants.com/Yellowopp/Acmella_oppositifolia_page.html.


I have on good authority that _A. repens_ is the current name (specialist consultation). I can return next week with the full explanation and a citation, as it was a bit confusing. Tropicos and the USDA site are good resources, but they aren't always up to date.

I'm not sure what to make of Dave's plant. Could be the same. I'll inquire.

http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242434785


----------



## Michael

I believe the plant in the photos is _Calyptocarpus vialis_, a.k.a. horse herb.


----------



## davemonkey

Cavan Allen said:


> Tropicos and the USDA site are good resources, but they aren't always up to date.


I second that. There are a few times I've found out-dated info on the USDA site.

Michael, that pretty much looks like it doesn't it? If that is indeed the case, the plant I have in my picotope may actually be the Calyptocarpus. I need to get with mudboots and see if his emersed sample has flowered for him yet.

The only thing that makes me think that it's Acmella I have in the tank is the fact that the Calyptocarpus is only a FAC (occurring on uplands as often as wetlands) and I have yet to encounter a FAC that will grow underwater.

Basically, it means I've been telling people where to find Acmella and in reality it is not Acmella...OOPS!


----------



## Michael

The specific characteristics that lead me to believe it is _Calyptocarpus_ are the shape of the ovary and disk flowers vs. the same structures in _Acmella_. And you are right, it would be *very* surprising if _Calyptocarpus_ would grow submerged!


----------



## HeyPK

Calyptocarpus seems close to the genus, _Bidens_. They both have those two-pronged 'sticktight' seeds. In central Mississippi _Bidens laevis_ has become abundant in the shallow water of ponds. There is a thread about it here.


----------



## mudboots

Glad to see this thread! When I originally aquired some "mystery plant" from davemonkey I guessed it as a Bidens, but he said he didn't think so. I've been waiting for it to bloom since then, and that's been a LOOOOONG time. I have recently tossed some into the garden pond outside, so maybe better chance for a floral structure and a positive ID then.

I've been calling it Spilanthes aka Acmella, but would be very satisfied if the specimens would allow for a positive ID. 

Davemonkey, do I understand correctly that you've already got the ID based on the collection you pulled from to toss me the expirementals? Maybe I read too fast, but would that mean that we have a Calyptocarpus growing submersed?


----------



## davemonkey

Mudboots,

No, I think what I had growing submersed, and what I subsequently gave to you is the Acmella. 

But when I saw the plant that I pictured in the first post, I mis-ID'd it in the field as Acmella (based on what the submerged plants look like) when in truth, the plants I see in the field are really Calyptocarpus. I have not actually tried to grow what I have seen out in the field yet. It is growing all over my yard so I suppose I can give it shot...give me a couple weeks to get it transitioned (if it will even do it) and I'll post pics if it turns out okay.

-Dave


----------



## Michael

If _Calyptocarpus_ will grow submerged, I really want to know about it. I love the plant in my garden, where I use it as a ground cover in dry shady areas where lawn will not grow.


----------



## davemonkey

Michael, 2 days in my tank now and aerial roots are forming. That's not a positive sign it will make it...but stay tuned...


----------



## Cavan Allen

OK, the name issue:

The type of _Acmella oppositifolia_ turned out to really be this plant:
http://www.tropicos.org/Name/2700871

So, _A. oppositifolia_ is really synonymous with the _Heliopsis_ species (in the link, look under synonyms). The name then falls to A. repens.


----------



## davemonkey

Cavan, thanks for that info. So, the "Acmella" plant I THOUGHT I had in my yard, and that I PROBABLY have in my picotope, would have correctly been _Acmella repens_ if I read that right...right?

Do you agree that the plant in my yard that I posted a pic of, however, is the _Calyptocarpus vialis_?


----------



## mudboots

I think that is correct David, that the yard plant is a _Calyptocarpus sp._, and would not likely make it submersed. BTW - the "_Acmella_" that I have continues to grow very fast, but still no floral structures for ID.


----------



## HeyPK

The Mississippi Acmella blooms most profusely in late fall. Are you giving yours a short day/long night regimen?


----------



## mudboots

No; it's on a long day / short night, but I 've got some that established well in my outdoor mini-pond, so I'll wait for it to show this fall.


----------



## davemonkey

_Calyptocarpus_ has failed to thrive and is officially dead in the aquarium.


----------



## Michael

Too bad, but thanks for letting us know.


----------

