Wednesday, 8 September 2021

Rosa Mollis Soft Downy rose

Rosa Mollis  Soft Downy Rose,  a search up North....

Having started last year to photograph wild Roses found in Cambridgeshire, a chance to see some more northern species in 2021 seemed a good idea. The Downy Roses are a difficult group and with photos taken of R. tomentosa and R. sherardii in Cambridgeshire, an obvious target was Rosa mollis, the Soft Downy Rose.  And I wanted to photograph the most 'pure' example , if any rose is ever 100% 'pure'.

Since my daughter is now living in Newcastle, research of the BSBI maps showed potential targets near Newcastle and also around Allendale Town, home of the other mollis, Crepis mollis the Northern Hawks-beard. I then moved on to Teesdale and Ingleborough.

First stop was the Gosforth Nature Reserve just to the North of Newcastle, an area of wetland and woodland. Having paid the £5 entry fee,  I headed down the track from the entrance hut and within 20meters found the target, next to a Dog Rose. Five pounds well spent!

R. mollis, 3rd July 2021, Boundary Ride, Gosforth Nature Reserve.

 The first thing to notice was the dull leaves, a feature shared with the other two Downy roses. More subtle, was the lack of arching branches, giving it a lower height despite some thick near vertical stems. Flowering was nearly over but a couple of flowers that were still showing, were a bright and quite deep pink. Time to get out the BSBI handbook on roses and check that its features actually all conformed.

According to the handbook, the first key feature of R. mollis is the straight patent prickles. Prickles can be variable on roses and don't always quite obey the rules, so it is worth checking more than one stem to get an overall impression.

Mature prickle on an older stem, is patent (sticking out at 90 degrees) and quite thin.
It has a large oval base and is not unlike the lowest example shown in the illustration in the handbook.

R. mollis. Patent, straight and thin prickle. 3rd July 2021

R. mollis, New growth prickle.

R. mollis, stem just below pedicle with narrow fine prickles.

These prickles all look good for Rosa mollis as they are a critical feature and later, on my journey, I found R. mollis which were not quite so pure and started to have more curved and thicker prickles.

The main feature is that they are very thin despite having a wide base and that they stick out straight at either 90 degrees or slightly upwards. A comparison shot of Sherard's Downy Rose follows which shows more tapering and curving. 

R. sherardii. New growth prickle. 9th July 2021.

Lealets.

R. mollis. Upper leaf which is quite dull and leaflets just about spaced apart.

R. mollis. Upper surface is hairy. Quite dense simple white hairs all over surface.


R. mollis. Underside of leaflet. Tomentose 
This photo does not quite show the tiny glandular hairs which are almost hidden by the thick white simple hairs. These glands are hard to see due to their small size.
Blown up section of previous photo which just about shows the glandular hairs on the veins and leaflet surface. These are much smaller than the glandular hairs on the leaflet margin.

 These small sized glandular hairs are a key separator from the Sweet Briar roses like R. rubiginosa which have glands twice the size at 0.1 to 0.12mm dia.

Next up is the leaflet margin which should be 'irregularly glandular-serrate' according to the handbook.
R. mollis. leaflet margin.

The margin is certainly irregular with a basic uni-serrate shape but with secondary tips and glandular hairs either forming tips of their own or just stuck on the edge. The handbook description seems perfect.

R. sherardii  Leaflet margin for comparison is rather similar.


R. mollis Petiole and rachis have both short simple white hairs and glandular hairs.

R . mollis. Leaflet stipule has glandular hairs along the margin.


Flowers

R. mollis. Deep pink colour and stigma cluster covers disc.

R. mollis. Stigma cluster covers disc and is about as high as it is wide, forming a dome.

R. mollis.  Sepals are almost simple with few tiny lobes and dense glandular hairs on the outside surface. Hypanthium and pedicle with stalked glandular hairs.

R. mollis. Sepals can be raised to an erect angle.

Pedicles are reported to be 0.5-1.5 cm in the handbook although the photo above shows one at about 2cm. Pedicle length always seems to be quite a variable feature and is supposed to be shorter in mollis than sherardii which has pedicles 1-1.5cm.     

With the above photos to confirm the details I was happy that this example at the Gosforth Nature Reserve is a good example of a Rosa mollis.  However I was lucky to start with such a conforming example and as I travelled on to Allendale and Teesdale the problems of hybrids became much more difficult plus the possibility of R. sherardii and its hybrids.

One plant at Teesdale looked good and  the a few more photos follow below:

R. mollis at Forest-in-Teesdale near the river.

Two key points here are, that the stigma cluster covers the disc and the sepals are almost simple with very limited lobes. This plus the low growth pattern without the arching stems are needed to confirm a R. mollis.  Quite a few plants were found that did not meet this test but still showed many features of mollis.

R. mollis at Forrest-in-Teesdale 

 Same plant as above photo showing quite a short pedicle with long stalked glandular hairs that are also on the hypanthium.

R. mollis type prickles present.

Also nearby were plants that had white flowers but otherwise did seem to tick all the mollis boxes.

R. mollis with white flowers. Forrest-in-Teesdale

Close up of flower showing the stigma cluster covering the disc.


Sepals almost simple.


The handbook does say that white flowered forms of R. mollis can occur and at Teesdale it would appear that both the deep pink and white forms occur.

Problem plants. The following are a few photos of plants that did not have all the required features.

Allendale Town plant.

The stigma cluster does not cover the disc. This and the fact that the prickles were not quite thin enough, suggested this was not a 'pure' mollis.
Allendale Town plant.


The plant was also too tall.  I am guessing maybe this plant is a hybrid possibly with R. canina but the real difficulty is that the shift in features gets close to sherardii which also has a slightly smaller stigma cluster and more curved prickles.  Sherardii is also a taller plant.  With all roses the problem of hybrids makes identification difficult. 
Allendale Town plant.

One feature that suggests a hybrid of R. mollis and R. canina rather than an example of R. sherardii is that the sepals are still quite simple without many lobes.  This plant would need expert attention well beyond my skill level.

Another problem plant was found in Allendale which had a lot of the features for R. mollis but did not have the right growth pattern with arching stems. It also had white flowers.



Not the required shape.

Many mollis type features present but sepals have more lobes than expected. 


Conclusion.

To record a Rosa mollis is not easy. It has features that are close to R. sherardii, so care is needed to make sure all the main features are correct to exclude hybrids and sherardii.  I was lucky that my first plant which I found at Gosforth,  had all the features, as described in the Rose handbook.  Later at Allendale I found more plants, but some were certainly not 'pure'. The only other species of rose present in the area that I found, was R. canina agg.  so I suspect the mollis that had a more canina growth pattern were hybrids with canina
My search for R. caesia Northern Dog Rose was not successful and it is interesting that there are few recent records for this species and one recent BSBI record was, when located,  not accurate as it did not have many of the required features.

Hopefully the above photos are a good representation of what a Rosa mollis should look like and enable others to identify this species.

The main feature of R. mollis are:-
1) Growth pattern, low (2m max) with older plants having near vertical thick stems but without arching stems.

2) Dull leaves, a feature shared with tomentosa and sherardii. Hairy on both surfaces.

3) Prickles that are thin and do not become much wider as you go to the base. The base is large, as if it supports a more normal canina type prickle. Prickles stick out at 90 degrees and are straight or almost straight. Not dense.

4) Sepals are almost simple without lobes ( actually single simple lobes are allowed) plus according to the handbook, can have leaf like extensions. Though I did not find that feature on the plants I found. These leaf like extensions are quite common in many species of rose, where the sepals turn into leaf like extensions suggesting that sepals and leaves are closely connected. 

5) Stigma cluster covers the whole disc or at least most of it whereas sherardii only covers 2/3rds. Both dome shaped unlike tomentosa which has a higher width to height ratio.

Pedicles are short but there is much overlap in this feature with sherardii. One thing I have learnt over the last year is that to determine a rose, you have to check all the features. Some plants tick nearly all the boxes but one feature might not be correct and then you have to re-check with more concentration on the details and take a bigger sample from different stems. Make sure it's the same plant, not two different species with interwoven shoots, which can also confuse.  

Peter Leonard
Rampton Cambridgeshire
11th July 2021



Friday, 9 July 2021

Rosa virginiana. Virginian Rose in Cambridgeshire.

Rosa virginiana.  Virginian Rose in Cambridgeshire.

On the 15th June 2021 the Cambridgeshire Flora Group were walking westwards along the Guided Bus Way from Oakington towards Over.  Just before the Northstowe/Longstanton station Alan Leslie spotted a rose with deep pink flowers and green leaves growing in the planted hedge on the north side of the path. Alan identified this rose as Rosa virginiana and is the first record for Cambridgeshire. The hedge has been planted as part of the Guided Bus Project from a 'hedge pack' which mainly contains hawthorn but has at regular intervals rose species, mainly Dog Rose R. canina plus less frequently Sweet Briar R. rubiginosa.

Somehow either by design or mistake the rather unusual American rose has been included in the 'hedge pack' and is now growing free in our countryside.  The Virginian Rose has escaped before in several counties and is included in the BSBI handbook No. 7 by G.G. Graham and A.L. Primavesi.

The following are a few photos to show the features of this American Rose and I include some links to papers on rose evolution.

R. virginiana. Deep pink flowers and green leaves.

R. virginiana. Bright green leaves.

The deep pink might suggest these plants have come from a cultivated form as the handbook suggest the flower colour can be pink to white. It also suggests that the cultivated forms sucker freely, whereas in more natural stock, suckers are few (according to the handbook). The five plants in the Busway hedge were all suckering freely.

R. virginiana. Stigmas in a low dome shape that covers the disc.


One of the first observations that made this rose stand out as odd, was the stigma dome which was very hairy (villous). In fresh flowers it was yellow but soon turns pink.


The stigma dome almost completely covers the disc.

Sepals narrow, more or less simple, with long fine tips, densely glandular beneath. The pedicle and hypanthium with long glandular hairs which were much longer than shown in the handbook illustration. The US literature says these glandular hairs are very variable and some plants can lack them completely.

This photo above shows that some sepals did have thin lobes, so some were not entire/simple.

Bracts on pedicle

Although not a important detail, the bracts are shown in the above photo. The centre pedicle has no bracts but the two side pedicles have a bract at the base plus two smaller bracts ranged oppositely about half way up the pedicle. These bracts did not hide the glandular hairs on the pedicles.  These bracts had sparse glandular tips along the margin.

R. virginiana. 

Pedicles were up to 4cm rather than the 0.8-1.5cm as stated in the handbook but the length of pedicles is always variable and the handbook uses average values. Not sure what he average length would be but certainly more than 2cm.

Young prickles,  slender, straight or curved.


Leaflet. Uni-serrate, glabrous.

 An interesting feature of this leaflet is that the teeth do not start at the leaflet base, so you have an entire margin to the first quarter without teeth. This is shown in the handbook illustration by Margaret Gold but is not commented on. This particular leaflet has 12 teeth on a side, which is a low count as a more typical count would be 18. This shows that teeth count is variable.  The average count should be 14 according to Bean, but my experience on these planted roses, is that teeth count is quite variable and some leaves are in some parts bi-serrate. Do you count the secondary tips?

Leaflet margin showing uni-serrate teeth and hydathodes on each tip. No glandular hairs.

In many ways this rose is quite familiar to our British roses. For example, the leaflet margin teeth having the temple dome shape, (convex then concave), as seen in R. arvensis and many R. canina.  A paper on the evolution of roses suggests the American roses have been long separated at 4.1 million years at least :-

'This means that among the extant species of American roses, only the species of R. subgen. Hesperhodos results from this ancestral widespread distribution while the other American species result from a later (at 13·4 Ma) re-colonization from Asia. Exchanges between western North America and eastern North America seem to persist even today. Exchanges between eastern North America and Asia were interrupted at 5·3 Ma but exchanges between western North America and Asia lasted longer and were finally interrupted at 4·1 Ma. '

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4551085/

R. virginiana. Leaflet stipule is large and wide and toothed.

Another stipule, sometimes edges can roll inwards to make it look thinner than it really is.


This feature of a wide stipule (especially at the leaf end) is one of the identification points that separate R. virginiana from the similar R. carolina which has only a narrow stipule.

  R. carolina also tends to have only 1-2 flowers per stem rather than the 3 or more in R. viginiana. The following site has details on how to tell these species apart.

ref :-     https://gobotany.nativeplanttrust.org/species/rosa/virginiana/

Native distribution from a paper on evolution of American roses which suggests separation of these species is not easy and the Americans face the same problems as European rose taxonomists.

Native distribution of R. virginiana by Simon Jolly

https://www.researchgate.net/publication/51196380_Polyploid_and_Hybrid_Evolution_in_Roses_East_of_the_Rocky_Mountains

Summary.

Although there are some discrepancies in the handbook description, compared to the roses shown here, like the stipules being narrow, (shown wide in the illustration by Margret Gold), I am happy that the plants found on the Guided Bus Way are Virginian Rose, which was a new species I was not expecting.  This species is available for sale in the UK.

Rose Site on Guided Bus Way

Plants at TL40696 67779,  TL40444 67879, TL4039494 67896, TL40375 67913 and TL40348 67922.

Peter Leonard

Rampton, Cambridgeshire.

30June 2021 

Ref:- G.G. Graham and A.L. Primavesi  Roses of Great Britain and Ireland. BSBI Handbook No. 7

Saturday, 12 June 2021

Early Forget-me-not, Myosotis ramosissima

Early Forget-me-not, Myosotis ramosissima 

A follow-on blog from my general blog on dry habitat 'Forget-me-nots July 2020' Myosotis ramosissima with attention to the sub-species ramosissima and globularis, using knowledge gained in Spring 2021. Both sub-species would appear to be present in Cambridgeshire. A comparison with M. arvensis is also included.

Summary and terminology.

M. ramosissima ssp. globularis. 19May2021, Cambridge, Norman Way.

Sub-species globularis has several differences from the sub-species ramosissima.

1) Flowers present almost to the base of stem.

2) Calyx is up to 2.5mm rather than up to 4mm in ssp. ramosissima.

3) Calyx lobes broadly triangular rather than narrowly triangular.

4) Corolla distinctly exceeding the calyx rather than scarcely exceeding the calyx.

Ref. Sell and Murrell, Flora of Great Britain and Ireland. Vol 3 Page 374.

In this particular plant as shown above, the stem leaves were limited to either one or two, with the highest being only 1 cm from the base. The inflorescence then continues 7cm beyond the top stem leaf. The stem leaves were at stem junctions.  

The length of the calyx was measured at 2-2.5mm and the calyx lobes are cut to slightly more than half way and are quite blunt tipped. The tips of the calyx fall short of the petals so you can see the corolla tube before it splits into the petals. The petals are held in a cone rather than being flat.

M. ramosissima ssp. globularis    Scale in mm

The above photo shows the calyx is just over 2mm in length and tends to have the calyx teeth slightly open in fruit. The corolla tube is easy to see with a gap between the calyx teeth tips and the petals. The  flower has a diameter of just under 2mm.

M. ramosissima ssp. ramosissima,  Gun Hill Dunes, North Norfolk. 3Jun2021

The tips of the calyces are touching the petals so there is no gap to show the corolla tube. The calyces are slightly more pointed than shown in ssp. globularis.  The length of the calyces were over 3mm.  This plant was found in the short turf of the dunes just west of Holkham Pines, Norfolk. 

M. arvensis. Fen Drayton, Cambs. 30May2021

Field Forget-me-not M. arvensis can look similar to M. ramosissima ssp. ramosissima  with no corolla gap but the pedicles are longer than the length of the calyx and so far, this has always been a clear difference.

M. ramosissima ssp. ramosissima. Newmarket. 18May2021

M. ramosissima ssp. ramosissima. Newmarket. 18May2021

Key points are the lack of corolla gap on the open flower, short pedicles supporting longer calyces.
Note the fading flower is starting to show the corolla tube so the presence of the gap should be taken from fully open flowers.


M. ramosissima ssp. globularis, Fen Drayton. 15May2021

Flowers present almost to base of stem although this may be a difficult feature to determine on some plants due to variation in growing structure. Corolla gap is clear. Note short pedicles.


Top plant is a M. ramosissima ssp. ramosissima from Cambridge North Station sidings and the lower plant is a M. arvensis. The stem leaves do go up the stem in both but the M. arvensis tends to have many more leaves and has a thicker stem. The pedicles are much longer in the M. arvensis. 15May2020.

Summary. Sometimes very small plants of Field Forget-me-not M. arvensis are hard to tell apart from Early Forget-me-nots M. ramosissima. Some knowledge of the two sub-species helps in distinguishing Early ramosissima from  Field M.arvensis. I thought at first that the corolla gap would be a good feature to distinguish them.  This hit a problem fairy quickly in that some ramosissima lacked the corolla gap and hence triggered an investigation of the literature.

 The two sub-species both have chromosomes 2n=48 and some plants will be intermediate. So far, on a limited sample, these two sub-species do seem to be consistently different, based on the four differences noted by Sell and Murell. 

Stace gives the sub-species name lebelii to the intermediates The difference in the shape of the calyces' lobes is very subtle and the structure of the plant can be be variable but the corolla gap and length of the calyces seem to hold up well. With a larger sample I would expect some intermediate plants to be found and it would be interesting to take samples from many sites and plot the corolla gap and length of calyx to get distributions. The pedicle length could be added as another parameter.

 What also seems to hold up very well, is the length of the pedicles in relation to the length of the calyces; being short in both sub-species. Often M. arvensis has clearly longer pedicles especially lower down the stem being equal or longer than the length of the calyx. 

 There is truth in the words in Sell that 'M. arvensis , ramosissima and sylvatica run into one another and are difficult to distinguish on precise characters but can usually be recognised in the field when all taxa involved have become familiar'.

Hopefully these photos will help in the identification of both versions of Early Forget-me-not.


Peter Leonard

Rampton, Cambridgeshire.

11June 2021

M. arvensis showing pedicle length equal or longer than calyx length.