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Yellow Oxalis: Oxalis corniculata

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#1 Adrian

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Posted 14 June 2021 - 10:23

Yellow Oxalis: Oxalis corniculata
I think this is the correct ID, but am willing to be corrected! ( I can add full floral details if ID is confirmed)
I have these plants growing in cracks on the ground around my house in Surrey, UK, but flowers are quite scarce and short lived. They are very small: max 10mm across. The leaves are a purple colour.

Technical details: Nikon D800 full spectrum conversion, 105mm UV Nikkor. Baader U filter. Bright sunshine, 1/2 second @ f/11, 400 ISO. White balanced in Photo Ninja using PTFE tape.
Visible light: As above with S8612 filter. 1/500th second @ f/11

Attached Images

  • Attached Image: Oxalis comp lo res.jpg

Adrian Davies
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#2 nfoto

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Posted 14 June 2021 - 11:06

Oxalis is a large genus with probably > 800 species, originating mainly from South America or South Africa. Many species are cultivated and these and others have become widespread elsewhere. Thus, I encountered a bewildering array of Oxalis spp. when visiting the Cape province in South Africa. Using a local flora helped me sort some of these to species, but not all of my material could be identified. The UV appearance of these varied from false-yellow "bulls-eye" to false blue or in some cases, even completely black rendition.

Oxalis corniculata is a highly variable species and the nomenclature is confused. Read more about this and other UK Oxalis species here: http://archive.bsbi....uk/Wats4p51.pdf

#3 colinbm

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Posted 14 June 2021 - 14:58

Nice examples Adrian, sharp too.

#4 OlDoinyo

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Posted 14 June 2021 - 17:35

These are called false shamrocks in America because the foliage somewhat resembles that of Trifolium dubium (which is not closely related.) You often see potted specimens on sale around St. Patrick's Day.

#5 Andrea B.

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Posted 14 June 2021 - 21:49

Looking in my Wild Flowers of Britain and Northern Europe on page 140, I see 4 yellow oxalis.

First is Oxalis corniculata having flowers 4-7 mm (petal length) with a sprawling, creeping habit and leaves which are often purplish about 8-15 mm.

Next is O. fontana, quite similar but with an upright habit.

Then there is O. exilis with tiny leaves only 2-6 mm.

Finally there is Oxalis pes-caprae, the "Bermuda Buttercup" which has flowers about 20-25 mm.

I'm going to go look at another reference.
A small edit to what I initially wrote involved my mis-observation of your flower size which you did clearly state!

[more info here later]
[here's more]
OK I looked at two other sources.
And here are some nice links..

Oxalis corniculata: https://www.ukwildfl...llow_sorrel.htm
Looks like Adrian's Oxalis. Has the brownish-purple leaves.

Oxalis exilis: https://www.ukwildfl...llow_sorrel.htm
No. Leaves all wrong.

Oxalis fontana: https://fleurs-fruit...lis_fontana.php
No. Leaves all wrong.

Oxalis pes-caprae: https://www.ukwildfl...a_buttercup.htm
No. Different habit with the umbel of flowers.




Adrian, I think you are quite safe going with Oxalis corniculata.
Very nice work.




Birna, thanks for the linked reference. Saved it!



Andrea G. Blum
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#6 Andrea B.

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Posted 14 June 2021 - 22:09

Reference:

Wildflowers of Britain and Northern Europe
Richard Fitter, Alastair Fitter, Marjorie Blamey
Fifth Edition 1996
HarperCollins Publishers, London.
Wood Sorrel Family, Oxalidaceae
Page 140 with illustrations on facing page 141.

This is an excellent field guide for British flowers.
Wonderful illustrations.
Andrea G. Blum
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#7 nfoto

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Posted 14 June 2021 - 23:16

The purple foliage tinted by anthocyanins are not specific to Oxalis corniculata. In fact, not even a characterstic of that species. Blame horticulturists and their bizarre ways.