Crepis foetida Subsp. rhoedifolia in Cambridgeshire.

Stinking Hawk's-beard Crepis foetida Subsp. rhoeadifolia in Cambridgeshire.

Crepis foetida subsp. rhoeadifolia

In late July the BSBI County Recorder, Jonathan Shanklin found an interesting Crepis at Hobson's  Park next to Addenbrooks Hospital. With the help from Alan Leslie and his vast library, it was identified as Crepis foetida subsp. rhoeadifolia.  Unlike the native species Crepis foetida subsp. foetida which hangs on at Dungeness and Rye, rhoeadifolia is a plant of  central and south-eastern Europe. One has to assume it arrived in a seed mix. This sub-species has not been recorded in Britain for many years.

The crepis group are complex, with a large number of species  displaying "reticulate evolution via hybridization across lineages or of incomplete lineage sorting".   Where have I heard of that before? Roses!

Anyway if you want to know about the genetics of Crepis foetida and other species in this group, a PHD thesis by a lady from Libya was done at the University of Giessen in Germany and its conclusions make interesting reading even if the detailed genetics are in my case, above my pay grade and understanding.

http://geb.uni-giessen.de/geb/volltexte/2017/12573/pdf/EsklualGhalia_2017_02_20.pdf

I think the conclusion of her work, is that Crepis foetida subsp. foetida and Crepis foetida subsp. rhoeadifolia should remain as sub-species but that the third subsp. Crepis foetida subsp. commutata should be regarded as a separate species Crepis commutata. 

Where both subspecies grow together, intermediates do occur. Having said that, in many places there are distinctive features that separate the two subspecies. Flower size is 20-30mm diameter in rhoeadifolia and 15-25mm in foetida, the outer phyllaries (involucral bracts) are longer in rhoeadifolia and also wider being 1-1.5mm wide against only up to 0.75mm in foetida. Both lack the translucent scales on the receptacle that are present on Crepis commutata.

Description.

First impressions were that this was not like any of the normal species found in Cambridge. The capitulum had a rather wide onion shape and it was still in flower at this late date. The flowers were up to 32mm in diameter, bright yellow with some red banding on outer ligules.  Plants had a basal rosette of leaves and several stems with few middle and upper leaves which branch to support the flower heads.

The first photo above shows structure and some flower buds are drooping, although at this stage most flowers are beyond the 'drooping in bud' stage and are held upright. The involucre, stems and leaves all had simple grey hairs which gave the plants a grey look.

The first plant, found beside the path with prominent white pappas extending well beyond the phyllaries.

Typical plant showing many upright stems and the greyish look.

 Crepis vesicaria ( Beaked Hawk's-beard) had long ago finished flowering and even its seed heads had lost their achenes. Crepis biennis (Rough Hawk's-beard), although later than vesicaria, had also finished flowering, except for a few late examples. Crepis capillaris (Smooth Hawk's-beard) was still in flower but with much smaller flowers.

Comparison of C. biennis  against Crepis foetida subsp. rhoeadifolia showing wide capitulum and 
very prominent white pappus. 25th July 2023. 

 Jonathan had also spotted that the outer achenes were a shorter length and less beaked compared to all the inner ones. This is a feature which excludes all native Crepis except for a sub-species of C. vesicaria called Stellata, a native of Morocco which according to Sell and Murrell, has been found in Cambridgeshire. There would be some doubt over this tentative identification, which is named subsp. gigantea in Alan Leslie's Flora of Cambridgeshire.  Stellata did not fit with the plants at Hobson's Park but it took some time to exclude it. It has according to Sell and Murell, involucral bracts with dense , long and short , greenish or dark glandular hairs. It also has discoloured stigma.

Achenes of subsp. rhoeadifolia.

The shorter outer achenes are clasped by the inner involucral bracts (phyllaries).  

Shorter outer achenes are held in the involucral bracts long after the longer achenes have blown away.
Note the cillate hairs on the receptacle. 

Flowers.

Note the yellow stigma matching the yellow of the ligules. Some darkening did occur as the flowers aged. The diameter of flowers was up to 33mm which fits the range of rhoeadifolia against foetida which has range 15-25mm.

Variation in the amount of straight simple white/grey hairs present on the phyllaries (involucral bracts) with most plants having quite dense white/grey hairs. The outer bracts are held quite close and some are quite long and the longest well over 50% of the inner bracts. This is another feature of the subspecies rhoeadifolia.

Outer bracts are very variable in length but the longest are well over 50% of the inner.

Phyllaries have simple grey hairs and cobwebby hairs. At this stage the phyllaries are starting to spread in the cup and saucer shape typical of some Crepis species.

Leaves.

Basal rosette of leaves.

The basal leaves of some Crepis species can be highly variable and highly complex. Crepis biennis ( Rough Hawk's-beard) being especially variable making leaf shape not very useful as an identification feature. It would appear that Crepis foetida has a more consistent basal leaf shape in that the basal leaves have a spade shaped tip which tapers down to its base, with triangular lobes at least for British illustrations of both sub-species. This may not be true over its whole range, as a publication on Bulgarian Flora has illustrations which show a much more irregular shape.

Mid Stem leaf . A more pointed version of the basal leaf.

Many hundred plants present at this site suggests it has been present for several years. It has also spread into the adjacent field.

Differences between the two sub-species foetida and rhoeadifolia. 

Not having seen foetida in the wild, puts me at a major disadvantage, so maybe next year a trip down to Rye in Sussex would be a good idea. Strangely, the re-introduction program of C. foetida subsp. foetida used plants grown at the Cambridge Botanic Gardens, however none seem to have escaped and the area around has been well covered over many years.

Rhoeadifolia can grow to 80cm whereas foetida is usually limited to 50cm. It would appear from photos of foetida at Dungeness and Rye, that it is often a smaller plant and may be greener and not so grey. Maybe the density of the grey hairs on the leaves, is a particular feature of the Hobson's Park population. 

C. foetida subsp. foetida

C. foetida subsp. rhoedifolia

Hopefully the above photos help to document this sub-species, which was a great find by Jonathan Shanklin and he has written up a short account for the April 2024 edition of BSBI News. 

Peter Leonard

Rampton, Cambridgeshire.

November 2023

 

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Identification of Roses, Leaf stipules.

Identification of Wild Roses, Leaf stipules. Based on new research by Tony O'Mahony.

Leaf of Rosa agrestis showing stipule.

In a recent major article by Tony O'Mahony in the Irish BSBI bulletin (ref 1), he found that Dog Roses in the subsection Caninae ( Canina, caesia, corymbifera and stylosa etc.), leaf stipules have a different gland type to that of other groups ( Rubiginosa and Vestitae.).

  His article covers many other new features but here, I thought I would illustrate the stipule gland feature, as it has been found to work well in Cambridgshire.

Warning. Dog Roses are a difficult group with features that not easy to separate into what are now regarded as 'species'. Recently British and European Dog Rose species have been aligned ( ref. 2) resulting in R. canina being split into three species, R. canina, R. corymbifera and R. squarrosa. Also the Northern Dog Rose R. caesia has been split into R. caesia and R. dumalis/vosagiaca. Unfortunately an updated BSBI Handbook has not appeared yet although I hear one is being written, so the BSBI Handbook No7 by Graham and Primavesi (ref. 3)is still the best source of information. Good though it is, it is now showing its age. New features that Tony O'Mahony has found are not covered.

The Species Problem.  Roses as a group do not fit into neat species. What now have been decided to be  'species' are hybrids that arose in the distant past from unknown parents and became stable and spread as ice ages came and went. Although 'stable' the evolutional splits and regroupings never reached the stage where different 'species' could not freely hybridise. In more recent times, although these old established 'species' are widespread, any local groupings of different 'species' will hybridise and sometimes produce viable offspring. The problem is particularly bad with the Group Caninae (Dog Roses) with their strange unbalanced combining of the parents genes (canina-type meiosis) plus frequent hybridisation. Reciculate lineages in evolution cause problems as most genetic analysis  assumes a branching tree of life to generate the relationships between species (Phenograms).  

As an amateur botanist without any formal training, I try and look at as many features of a rose as I can cope with and see if they all fit the somewhat basic descriptions in the handbook. Some plants fit well but many have aberrant features, which indicate they are not quite right for a perfect example of that species. The additional feature of stipule glands can help to confirm a good fit but can also show a Dog rose which was thought to be a straight forward R. canina but is in fact hiding some genes from, say a Sweet Briar. The stipule glands are however a useful identification tool to add to the range of feature that should be considered.

The New Feature.

Tony O'Mahony spotted that Dog Roses ( Subgroup Caninae) have stipule glands that are not round but elongated and also are feebly attached and therefore quickly detach leaving older leaves to have none left on the margin. Often these glands are well spaced on the margin and forward pointing.

Subsections Vestige ( R. mollis, sherardii, tomentosa, villosa) and Rubiginosa ( R. agrestis, micrantha, rubiginosa) have have stipule margin glands on stout stipes ( stalks) , the stipes are patent and permanently attached. Each gland is round in shape and when fresh, full of volatile oils, often red in colour. Strangely they often have a larger one, then a smaller, then a larger one along the margin and can be quite dense.

A) Dog Roses.

Rosa canina, close up of elongated glands on stipule margin near the tip.

Rosa canina. Rampton 31Jul23. Elongated glands and also missing ones which have got detached.

Note that the elongated glands on the stipule margin are different from the petiole glands (leaf stalk) which are stalked and round tipped.

R. corymbifera. Even when dried out the glandular tips of this Dog rose are clearly elongated and in this example, on forward pointing tips. 27th July 23. Cambridgeshire.

Dog Rose. R. canina . 7Jun23 Devils Ditch, Cambridgeshire

The photo above shows elongated glands which are mainly forward pointing and also sections of the stipule margin that have lost their glands even at this time in June. 

R. canina with possibly some caesia in it. Allendale, 21Jul23 

Above photo included to give a bit more geographic range ( Northumberland) to these photos. A dog rose that had mixed features of canina and caesia and therefore regarded as a hybrid.   It does show forward pointing glands, which even though dried are elongated, although the smaller ones do appear to be more rounded. It is possible that this particular rose has a more complex history and is not 100% a dog rose. It would seem that the Dog Roses can also have the big, small, big gland pattern but what that means is unclear.

Another canina/caesia hybrid, Fen Drayton, Cambridgeshire, 

Clearly elongated glands but not as forward pointing as one might expect. Interestedly the larger elongated glands are interspersed with smaller sessile glands. This does seem to occur in some examples of Dog Rose.

R. stylosa. slightly dried but still elongated and forward pointing.
25 Jul23 Comberton , Cambridgeshire.

It is interesting that although R. stylosa is held within the Subsection Caninae it is often regarded as not being a Dog Rose yet it still displays the elongated forward pointing glands. It does show some variation in size with the big, small, big pattern, seen in the non Dog rose groups but also in some Dog Roses. 

B) Non Dog Roses.

R. rubiginosa. Fresh round glands on short stalks, patent not pointing forward.
25th July 23 Comberton, Cambridgeshire.

This example shows the big, small, big alternate sized glands, the smaller being sessile.

R. sherardii, 23 Jul 23. A11 junction near Duxford.

 A non Dog Rose in that rounded glands, not forward pointing, dense along margin and displaying the big, small, big pattern. 

Conclusion.

It would appear that there is a difference between Dog roses and non Dog roses when it comes to stipule gland shape. The forward pointing and big, small, big features seem more random. What works in County Cork seems to work here in Cambridgeshire. 

There are problems in that the Dog roses have often lost all their  glands but usually it is possible to find a new leaf on a late non flowering shoot which may have glands left. The gland shape can be seen with a X10 or X15 magnifier.  The paper by Tony O'Mahony is linked below and he has to be congratulated on highlighting this new feature.  

Ref 1,  Irish BSBI News No 33 Page 5  by Tony O'Mahony

https://bsbi.org/wp-content/uploads/dlm_uploads/2023/05/IBN-2023-V2.pdf

Ref 2, 

Dog-roses (Rosa sect. Caninae): towards a consensus taxonomy, Piet Bakker, Bert Maes, Roger Maskew, Clive Stace.

https://britishandirishbotany.org/index.php/bib/article/view/10

Ref 3, Roses of Great Britain and Ireland by G.G. Graham and A.L. Primavesi BSBI Handbook No 7 1993

Peter Leonard

Rampton, Cambridgeshire

10 Aug 2023

Update 29th August 2023.

Roses are never going to be easy and today in Hayley Wood we found a rose that would appear to be a dog rose with no glands on the pedicle and might fit the group Dumales/ R. squarosa, but had round glands on the leaf stipule. This and another similar plant nearby seems to break the rule and can only wonder what this means in terms of its parents. This combination of Dog Rose features and round glands on the leaf stipule is not common as several hundred roses up to this point had conformed to the suggestions by Tony O'Mahony. I can only assume this is down to a more complex history with some hybridisation to a non-caninia type rose. A few photos follow.

Dog Rose, R. squarrosa Hayley Wood. 29th Aug 23

A rule breaking example of a Dog Rose showing round stipule glands.

Dog Rose , Hayley Wood , with round leaf stipule glands. The hip is more rounded than typical Dog Roses found in Hayley Wood which might indicate a more complex history.

Dog Rose at Hayley Wood, with round leaf stipules glands. The orifice is narrow as expected and the disc almost flat to slightly convex. Many of the Dog roses in Hayley Wood have a much more convex disc.