How to distinguish similar species of Hydrocotyle?

Recently I uploaded a collection of plant images. It should be “铜钱草, money plant” in Chinese. I used to believe its latin name is “Hydrocotyle vulgaris”. However, iNat gave another opinion ---- "“Hydrocotyle umbellata” with similar features.
I tried searching the diffenence of these two species but failed. I cannot find any difference between images given by search engine.
So, how to distinguish similar species? Especially when documents are limited.
Thanks. : )

1 Like

I also can’t find any resource with desription of two of them, the only thing I saw is umbellata originated in Americas but was introduced in Old World.

QwQ I find one more similar species: Hydrocotyle verticillata

There are 4 species with similar features in total now. Hydrocotyle umbellata, Hydrocotyle verticillata, Hydrocotyle bonariensis, Hydrocotyle vulgaris.
Not only these species, some genus includes many similar species, like Aconitum sp.. How to distinguish them properly?

Which Aconitum you refer to? Cause all sp. I know have leaves with completely different structure that Hydrocotyle, you can see lobes that are abcent in the latter.
verticillata is mentioned as a small plant up to 10cm high and lives only underwater, and it is not popular so less likely o find away from initial range. bonariensis is up to 25cm found on the water surface or ground and needs higher temperature (20C+).

Want me to add some more? In north america we also get H. tribotrys.

Distinguishing between two species which don’t naturally occur together is often quite difficult, even for a trained botanist. Most of the reference materials available for identification of wild plants only treats plants within a distinct geographic area and will tell you the characters to distinguish between only those plants. Often the best way to separate them is to look at preserved specimens in herbaria and see if you can find a difference yourself if they’re really similar and pictures aren’t useful, but most people cannot do this.

With your plant in particular, the inflorescence is verticilate with eliminates H. umbellata right away. Looking at pictures of H. vulgaris on iNat shows the flower stalk is shorter and is generally under the leaves and the flowers are on very short pedicels (compared to long on yours) which indicates to me that your plant is going to be H. verticillata.

I’m not sure if my process there makes sense, but I’ve also spent a bunch of time reading about these species so I know that the ways to tell them apart are only based on the flowers and the leaves are basically uninformative since they look the same in all the species you’ve listed. And with the flowers whether the inflorescence is verticilate or umbellate, and then whether the flowers are stalked or not.


Normally, organisms are not evolved to be distinguished morphologically. In many cases photos lack the information to distinguish the organism to species level, and some species (such as cryptic species) may only be distinguished through DNA sequencing. So just try to accept an ID at higher level like genus, family, etc.


@sunRuikang, there is a technical key to the Chinese Hydrocotyle at That may be more information than you wanted, but it might help!


One thing that can be confusing to users of iNaturalist is that the automatic AI robot can only identify species it has been trained on, which is usually a few common species in a genus. If you give it an image of something it hasn’t been trained on, it will often suggest the most similar common species. We are sure that a lot of rare or unusual species are being mis-classified this way. The hope is that this will improve over time, but it’s definitely a problem with iNaturalist as an identification tool.


In some cases it’s impossible without access to a laboratory.

For certain species range is the only avenue available to the non-professional observer.

Often you have to leave the genus at genus (or even family) level and accept the fact that it may be impossible to distinguish beyond that without access specialized equipment or extreme macro photographs of specific portions of the anatomy, as well as the knowledge of how to interpret those.


Welcome to the Forum! I don’t know much about plants, but often with moths it is not possible to ID different species without looking at genitalia under a microscope. Since this is a visual site, that is not possible, so a number of ‘Complexes’ have been created. They consist of two or more moths which are visually similar. I don’t know if plant species have such a thing, but visual ID can be tricky.

Thanks for your reply!
This question is because these plant are popular and cheap (3CNY including shipping) pet plant. I bought online and wondered what species it is but find so many possibilities. lol ; )


Thanks for your reply!
What makes me crazy is that even Wikipedia and academic essays do not give an answer on the difference. Maybe I can look up iNat database, but, I am not sure if these images are that exact with reliable resources.

Thanks for your reply!
So is there any source to find DNA featured sequence of rare species? GenBank?

Thanks, that is helpful.

Thanks, maybe in the near future DNA sequencing will be cheaper and easier. That might be the only solution. : )

Thanks, I really enjoy this opensource and friendly community. I have contributed many observation images hidden in my disk.


On genetic data this paper comes as one of first links: I think there may be genetic works on other species too.

From what I have learnt delving into Hong Kong lepidoptera IDing, it is a case of looking at multiple images and then spotting the differences (which can be extremely subtle), and then making sure those differences are consistent (whilst keeping in mind red herrings such as forms and aberrations).

Of course the caveat is to use observations with RG grades identified by reliable users (and in Hong Kong we are lucky to have a few experts), but in general the above practice can be a good way to hone those abilities. The advantage is once you are used to that then in the future you will then have more knowledge about where to look and what to look for when trying to distinguish between similar species.

And then as others have stated above, in many cases one cannot identify to species level in the field, and the specimen must be dissected in the lab.

Edit: And then another thing which is helpful is to have a piece of relevant text which contains a key that helps the reader to identify a specimen.

Yea that’s what I was saying before, it’s mostly because they’re not going to co occur with eachother. Even then, wikipedia often doesn’t have information for telling how to distinguish species. Sometimes when I’m writing articles I’ll throw a paragraph in about distinguishing two similar species, but most articles don’t have that information.

I’d also say that most plants can be identified using gross anatomy and a descent picture of the flowers. There are plenty of species complexes in plants too, and for those you need pictures of some sort of specific anatomy, like the base of the leaf, of the hairs on the stem or fruit. These types of pictures are often not attainable without a microscope or macro lens which can often make ID of these groups on iNat impossible. Grasses especially haha