Utricularia vulgaris and U. australis

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As there had been a lot of confusion how to distinguish the two freely floating European species of Utricularia, I try to illustrate this in the present post.

First said, it is nearly impossible to distinguish U. australis from U. vulgaris by vegetative means only. Although U. vulgaris generally tends to be more robust and bigger in overall size, and usually has more segments and traps per leaf, both species show a lot of variation of their size range.

Habitat preference may help a little bit, but both species will readily grow under the same conditions as well (however they never seem to grow sympatrically, at least in none of the sites in Germany I know of). Both species prefer clean, nutrient poor water that is rich in minerals and CO2. Utricularia australis usually seems to like more acidic water conditions, and thrives well in drainage ditches and pools of peat bogs, however can grow in any other type of water as well, including fish ponds, lakes, etc with a relatively high pH-value. In case of U. vulgaris, it’s the other way round, i.e. it grows preferably in high pH conditions, but can be found in acidic waters as well (especially in Northern Europe).


Utricularia australis growing in a mesotrophic fish pond in Southern Germany, together with water lilies and Potamogeton.


The same species growing in a small ditch of a sphagnum peat bog.

But both species can be readily told apart from each other by a set of floral characters illustrated below:

Most easily: in case you find developing or ripe seed capsules on your plant, then it’s U. vulgaris. Utricularia australis is sterile and does not produce any seed capsules (apart from some populations of smaller plants in Japan, which have been named U. australis var. tenuicaulis or U. tenuicaulis). This is because U. australis is a sterile palnt originating from a natural hybrid between U. macrorhiza and U. tenuicaulis most likely from Japan, and from there it spread all over Eurasia and Australia (hybrid vigour!)

In U. vulgaris, the pedicels conspicuously bend down in fruit, whereas in U. australis, the pedicels are kept upright even after the corolla dropped.


Note the fuiting pedicels of U. vulgaris.


Flower scape of U. vulgaris with reflection in the water.

The flower itself is a good character to tell both species apart as well:





Side view: in U. australis, the upper and the lower corolla lip form more or less a right angle or even an obtuse angle. In contrast, in U. vulgaris the two corolla lips form an acute angle, and the palate of the lower lip is firmly appressed to the upper corolla lip. In order to illustrate what I intend to explain, I indicated the angles I was talking about by the red lines in the above picture ;).





Front view: the lower lip of U. australis is always more or less even, the margin is spread horizontally. In U. vulgaris, the lower lip is distinctly curved downwards, i.e. the margin is reflexed.

Another character that is easy to observe in the field is the relative length of the pedicel in flower, compared to the length of the bract:


In U. australis, the pedicel is distinctly longer than in U. vulgaris, and it is about 3 to 5 times as long as the floral bract. The length of the bract is indicated by a bracket (;)) in the picture above, and the length of the pedicel by the blue lines. In the plant on the left, the pedicel is 4 times the length of the bract, thus it has to be U. australis.

U. vulgaris has much shorter pedicels, which are only 2 to 3 times as long as the bract (right).

The shape of the spur and the distribution pattern of nectar glands in the spur are further good characters to distinguish the two species, but both of them are more difficult to observe in the field and are rahter a good tool to ID flat pressed herbarium specimens ;)

The presence of absence and number of red veins on the palate is not a good character at all, as it varies greatly within both species.

I hope this draft picture guide helps a little bit to avoid further misidentifications ;)

All the best,


PS: Thanks to Martin for urging me to write this topic! ;)

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OMG Its 2.10 a.m here in germany and acually i wanted to go to bed but after i saw a Topic by you Andreas i had to read it haha

Danke danke für diese mega ausführliche Unterscheidung. Ist richtig richtig gut geworden! :)

P.s.: Martin muss dich öfters zu was zwingen, sowas zu schreiben :shock:

on english: thanks for this great guide to distinguish those two Utris :)

P.s: Martin should urge you way more often to write topics like this

Edited by Marcel B.
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Very nice report. I will recommand it to people.

I have never seen Utricularia vulgaris in the wild, so good way to identify it and try to find it.

Just another question to make this post more complete: can you please indicate the phytosociology to each of this species?

Edited by kisscool_38
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Thanks Andreas :shock:

2.04 am? Eight in the morning would have been early enough ;-)

The form of the lower corolla is indeed a good feature to distinguish those two. But the rest is not that simple for me as you say above :red33:

Fruits downwards? Hmmm


And the pedicels...


Here it looks as if australis has the shorter pedicels. OK the bract in australis is definately shorter... a bit shorter...

But taken into account that these are ideal type pictures to show the differences, I guess the bandwith of variability in the field makes it not that easy?

I think you need both : a good guide and experience in the field.

Thanks for your help - makes a very interesting subject complete now :shock:


Edited by Martin Hingst
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Hi Andreas,

Part 1 is my best guide on my local trips here in Belgium , thanks a lot for your second part.

Very useful and detailed paraphrase about their flowers!!!! Well done.



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as I said in the german forum: Very nice topic! I think that I will need it on my vacation (I hope that I find some Utricularia...).

Thank you very much! :shock:



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