Rosa sherardii. Sherard's Downy Rose in Cambridgeshire

Rosa sherardii. Sherard's Downy Rose in Cambridgeshire.

This blog shows a few photographs taken in my quest to learn about roses to be found in Cambridegeshire during the summer of 2020. 

According to the 'Flora of Cambridgeshire',  Alan Leslie 2019, there is only one current place where this species is found-  by the A11 at Four Went Ways. There were other records in the past in other locations but some were later considered to actually be Rosa tomentosa (Harsh Downy Rose), which suggests that telling these two species apart is not easy. 

Both these downy roses are in the section Caninae which mean they have the unbalanced breeding system in which the female parent contributes four sets of chromosomes to the progeny, whereas only one set comes from the pollen (male) which fertilises it. All these roses hybridise now and it is thought that all the current stabilised species today, were derived by hybridisation in the distant past.  The Downy roses are in sub-section Vestitae  which also includes R. mollis (Soft Downy Rose) which is a more northern species as far as the UK goes. R. mollis is not found in Cambridgeshire, nearest place being the Peak District. 

R. sherardii, 12 June2020, Four Went Ways.

First comment on this flower is the deep pink colour. The only other rose that gets close to this deep pink in Cambridgeshire would be R. rubiginosa (Sweet Briar). 

R. rubiginosa 10Jun2020 Devils Ditch. Reach.

R. tormentosa has a much paler pink flower.

R. tomentosa, 9Jun2020, 

Flower colour is not the most important feature that separates the Downy roses, which is the hairy leaflets. Flower colour in R sherardii according to the 'Roses of Great Britain and Ireland' BSBI Handbook No 7 by Graham and Primavesi (which is the standard reference) can be white in Scotland.  

R. sherardii, 12Jun2020, underside of leaflet.

The underside of the leaflets is densely hairy, a feature sherardii shares with tomentosa. It also has lots of glandular hairs which in the case of the sherardii at Four Went Ways are easy to see. In some tomentosa it is even more densely covered in hairs so that it is difficult to see the tiny glandular hairs. The density of these glandular hairs can be variable according to the literature.

R. tomentosa 19Jun2020. 

R. tomentosa 19Jun2020. Just a very few glandular hairs only just visible amongst the hairs.

R. rubiginosa has lots of glandular hairs but the glands are much larger and the density of the simple white hairs is less. The diameter of the largest glands is 0.1-0.12mm whereas the Downy roses have glands 0.05mm diameter and can also have a stalk. This is according to the handbook and was confirmed using a calibrated magnifier.

R rubiginosa showing stalked glandular hairs on underside of leaf. 15Aug2020 Swavesey.

R. rubiginosa Underside of leaflet showing glandular hairs and simple hairs.

Leaves.

R. sherardii,  note simple hairs on upper surface and glandular margin.

R. sherardii, 12Jun2020 Upper side of leaf.

R. sherardii, Underside of leaf.

R. sherardii, 12Jun2020. Stipule at base of leaf.

The particular group of Sherard's Downy Roses at Four Went Ways has an abundance of red glandular hairs. This is not always the case as I discovered when I visited Cork, Ireland in September. The stipule above has the normal glands along the margin but also all over the lower surface, whereas in Cork the glandular hairs just ran along the margin like many other species of rose.

 The leaflet stem ( petiole and rachis) have glandular hairs plus white simple hairs.

R.sherardii, 12Jun2020. Leaf edge.

The leaflet margin can be described as Multi-serrate with stalked glandular hairs having tips of their own in some cases. According to the handbook, R. sherardii can show quite a lot of regional variation, so sometimes the the underside of the leaflet can almost lack the soft white hairs and the glands.

R sherardii, 12Jun2020, Four Went Ways

The photo above shows the top of the flower stem (pedicle) and hypanthium (hip) with with long glandular tipped hairs. In this population the ball like tips are a deep red colour. To the right of the pedicle is a bract which also has lots of red tipped short glandular hairs on the margin and across much of its surface.

R. tomentosa. 22Jun2020 

Comparison shot of R. tomentosa showing the pedicle and hypanium have the same long glandular hairs.

The stipule has red tipped short glandular hairs along the margin like many species of rose.

R. tomentosa 24Jun2020 Post flowering photo showing pedicle, hypanium and sepals.

R. sherardii 12Jun2020  Post flowering photo showing pedicle, hypanium and pinnate sepals.

Not a lot to choose between these photos of the pedicle, hypanium and glandular hairs, as many of the features are similar. The stalk ( pedicle) for R. sherardii is supposed to be shorter 1-1.5cm compared to R. tomentosa at (1.5)2-3.5cm but I am not sure how reliable pedicle length is, as in my limited experience pedicle length can vary a lot even on a single stem.  

R sherardii, 12Jun2020 stigma cluster.

The stigma cluster is large, almost covering the disc - to 2/3rds- and domed with a few hairs. The disc is almost flat.

R. tomentosa 19Jun2020 Stigma cluster.

The stigma cluster is smaller so you can see more of the disc. It is taller and less domed in shape but also has the odd hair (many to none).  Disc is almost flat. This is a subtle feature and it would be interesting to take more photos of each species at more sites, to see if there is a consistent difference.

R. sherardii, 1Sep2020, Rounded hips have very deep red colour. 

R. canina Dog Rose, 1Sep2020 comparison shot.

Note the sepals remain on the R. sherardii whereas they have fallen on the Dog Rose at this stage. The R. sherardii are an amazing deep red which is not really shown to its full extent by the photos. Below is R. tomentosa which, according to the Handbook, should have lost its sepals by this stage of the hip turning red. It has previously been noted by Chris Preston in his review of The genus Rosa in Cambridgeshire (v.c. 29) an interim account, that some local bushes of R. tomentosa have persistent sepals. 

R. tomentosa. 14Oct2020

R. sherardii, 15Sep2020 Castletownbere, West Cork , Ireland

Final photo shows the shiny round red hips as the season comes to an end. They are not always so round in shape. By this stage the glandular hairs have lost their red tips which have turned grey and dried up. 

Conclusion. 

In my first season of looking at roses I think I can identify the two downy roses, R sherardii and tomentosa but need to be careful of hybrids. It is easy to miss the slightly aberrant features of hybrids, which require expertise beyond one season's learning.  Also I have little experience of regional variation which is a feature of R. sherardii, so more to learn plus I have not seen R. mollis yet. Hope to travel north to find R. mollis when lockdown is over in June.

Peter Leonard

Rampton, Cambridgeshire.

10th March 2021

R. tomentosa stigma cluster slightly taller than wide. Devils Ditch

R. tomentosa, Ditton Park Wood. 24Jun21

R. tomentosa 22Jun21. Devils Ditch

R. sherardii , flat disc, hairy stigma covering about half the disc at this stage.
Note pinnate side lobes, with two on the left sepal side in view.

R. sherardii, domed stigma cluster not as tall as R. tomentosa, Cambridge, Four Went Ways

R, sherardii Stigma cluster about as wide as tall.

Variation in prickles.

R. sherardii, almost straight.

R. sherardii, a more curved example. Shape slightly concerning but it is good to check several stems and see how much variation is present. This plant had mainly straighter prickles.

R. sherardii. Younger prickles.

R. sherardii, younger prickles.

The handbook suggests that although normally the prickles have weak bases some populations have stronger more curved prickles. The above prickle photos were all taken at Four Went Ways.

The variation in prickles from being thin and straight ad patent through to curved with slightly thicker bases is important as R. mollis has all prickles thin, straight and patent. It is worth checking several stems to see how much variation occurs.

For R. mollis see new blog under Rose label.