A yellow-flowered plant growing by the edge of a pavement.
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Can anyone tell me how to differentiate between Crepis vesicaria and C. capillaris before the fruits are ripe, please?
... the capitula of C. capillaris are 10-15mm in diameter and those of C. vesicaria are 15-25mm in diameter.
I don't know whether this is a reliable discriminant, but the illustrations in Streeter show the outer phyllaries in C. capillaris as much less prominent.
[I want a means of distinguishing them which doesn't require checking fruits under a hand lens - even if you wait to fruiting time it's a bit impracticable to keep checking fruits in the hope of finding a C. vesicaria. If I can find candidates by some other method then using the fruit character as confirmation would be OK.]
Poland says that C. vesicaria has bitter bluish-white latex. We tested this the other day, my friend confirms that it's bitter! But he doesn't mention latex for C. capillaris. He also uses a sagittate base to the stem leaves as a discriminator (capillaris present, vesicaria absent). Didn't notice in our specimen, and can't see in this observation.
Although it's not foolproof (and the size of the flower heads although a good indicator is not foolproof either - C. capillaris can have heads as large as 2.5cm as well) there are two fairly good jizz characters which are usable. C. capillaris has the short outer bracts more or less appressed and without scarious margins. C. vesicaria, as one can see from the photo, has the outer bracts spreading and with scarious margins.
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