Rosa squarrosa ( Glandular Dog-rose) in Cambridgeshire

Rosa squarrosa ( Glandular Dog-rose) in Cambridgeshire.

Now that Dog Rose R. canina aggregate  has been split into three separate species and documented in a new BSBI handbook, Wild Roses of Great Britain and Ireland by Roger Maskew and Gareth Knass, BSBI Handbook no 26, I thought I would try and find a Rosa squarrosa to photograph.

Glandular Dog-rose, R. squarrosa, 17th June 26, Cambridgeshire.

Previously R. squarrosa was regarded as a subspecies of R. canina under the sub-species group Dumales.

 R. canina agg. is now split into three species ( Canina, corymbifera and squarrosa ). This creates the complication of defining each of the hybrids between them and also the Northern Dog-rose,  which has also been split into R. vosagiaca (Glaucous Dog-rose)and R. caesia (Northern Dog-rose). 

This particular plant was surprisingly green but I would not assume this is a characteristic of squarrosa or any other dog-rose.

The first characteristic feature I check is the pedicel ( flower stalk below the hypanthium (hip)) as dog- roses should have a clean stalk without any glands, which is the case here. 

The sepals are pinnate with a few glands. They are reflexed even at this early post flower stage, which  fits with squarrosa, canina and corymbifera. At this early stage, just after flowering, sepals are moving from their flowering position of being out and downward, pointing at about 45 degrees. Timing of the sepal movement seems to be quite variable and sepal position is normally looked at later when the hips have turned red.   In this particular example the sepals have moved to a reflexed position quickly.

Hypanthium, sepals, and pedicels. Group of two hips on long pedicels.

The photo below shows the sepal with pinnate lobes, which have glandular tipped side projections and also a leaflike extension. Despite R. squarrosa being glabrous (no hairs), hairs are allowed on the sepals and on the stigma cluster.

The photo below shows the disc and stigma/styles. The disc is quite conical which is common in Rosa canina and I assume can often occur in squarrosa. The stigma covers about half the conical disc and has some short hairs visible.

Other characteristics are that, the pedicels were between 1 to 2cm against a handbook range of 0.8-2cm, so that's OK, although I don't find pedicel length reliable as it seems to vary a lot even on the same bush. Extremely short or long pedicels are worth noting.

  The orifice was small at about or less than a 1/5th of the disc diameter. Note the long thin hole that the stigma threads pass through and its gradual opening out into the hip capsule. One of the few criticisms of the old handbook was the drawing of the R. canina sectioned hip by Margaret Gold, which showed a rapidly opening orifice inside. This is not typical of R. canina and I suspect the sample  she was given  may have satisfied the characteristics of R. canina, but had some Northern Dog-rose in it. Overall her drawings were really very good and in some cases better than the photos used in the new handbook.

Cut hypanthium showing orifice and domed disc. R. squarrosa

An example of an atypical orifice suggesting hybrid with Northern Dog-rose or just a variation due to the flat disc?.

Also a very round shape to the hypanthium/hip.  Hip shape is variable according to the new handbook including spherical, although in Cambridgeshire I speculate that a spherical hip may suggest some hybrid influence.  Hard to prove though.

An example of a canina type orifice with a almost flat disc.

Next up is to look at a leaf.

Leaflets 5-7 and broadly ovate to ovate-lanceolate, acute or subacute, rounded at base, according to the new handbook.     The leaves shown below are not drawn out to an attenuated tip, are well spaced and are hairless, as required, to be conforming with squarrosa. Tony O'Mahony, a rose expert from Ireland, has noted that leaf shape is highly variable in R. canina and this is probably true for R. squarrosa. 

'This field study revealed that the only common denominators between the various R. canina populations, was that they all displayed glabrous, non-glandular foliage.

Yet, in stark contrast to these two points of uniformity, was the remarkable fact that the

leaves of this species proved bewilderingly polymorphic, my observations recording

considerable morphological plasticity in leaflet shape, dimensions, toothing, texture and

colour – not only between populations, but often between individual, adjacent bushes in

hedgebanks and hedgerows. Moreover, no correlation could be found between these leaf

forms and other features of these bushes. '

This insight from Tony O'Mahony is really useful and it's pity that the new handbook does not highlight such information.

R. squarrosa.

Another important feature I look at, is the leaf stipule glands, a feature not mentioned in the new handbook, but which has been found to be really important. See previous blog on this feature, Identification of Roses, Leaf Stipules. 

Leaf stipule showing dense glands still present and mainly round in shape with only the occasional elongated gland. This is a bit odd as the dog-roses should have glands that fall off quickly and are elongated in shape. These are staying on and are mainly round balls, not the elongated shape. When confronted with a feature that does not quite fit, a larger sample should be looked at, ideally from more than one major stem.  

The petiole (leaf stem) is also shown in this photo and shows a lot of stalked glandular protrusions. The glandular protrusions being a key feature of R. squarrosa. Note also no soft hairs.

Next photo is of the rachis which also has lots of stalked red glands. Ignore the fibres brought in by the wind but note the rachis has no soft hairs.

The major feature of R. squarrosa is that it has no hairs (except on the styles and sepals), being glabrous. The stalked glands are not included as hairs.  Below is a photo of the rachis of R. corymbifera showing the dense soft hairs which are its key feature.

   R. corymbifera rachis with dense soft hairs. 

Back to my potential R. squarrosa. Next check leaf margin.

Leaf margin showing bi-serrate edge with the secondary tips having short stalked and sessile red  round glands. The primary tips have hydathodes which are conical in shape and lack the liquid ball, unlike the round glandular tips on the secondary tips. Note the hydathodes have veins running to them.

According to the new handbook R. squarrosa can have either bi-serrate to multi-serrate margins. 

The underside of the leaf is glabrous, not a hair to be seen even on the midrib, just the occasional stalked red gland.

Prickles of R. squarrosa.

Conclusion.

This particular plant matches the expected features of what a Rosa squarrosa should look like, with the only aberrant feature being the round, more permanent glands on the stipules. This does suggest a slight introgression in the past with a Sweet Briar or a Downy Rose but no other sign of this was apparent. The bright green colour of the leaves was also unusual. 

 I think this plant could be regarded as belonging to the species as defined by the new handbook and we don't need to investigate further hybrids. A small amount of introgression is acceptable. The most common hybrid would be with Northern Dog-rose now split into R. caesia and R. vosagiaca.

The hybrid with either of the Northern Dog-roses would tend to show reddish stems, which were completely lacking in the plant described above. The new handbook says R. squarrosa, 'often strongly red-pigmented in open habitats in late summer' so the red stems appear to be an unreliable feature?

The influence of either caesia or vosagiaca would tend to have groups of hips (3-4)  on unusually short pedicels with large bracts that obscure the pedicels and large hips, densely hairy styles forming a dome-shaped head and blue-green back to the leaflets.

The plant above had 1-2(3) hips with longer pedicels. The pedicels were towards the 2cm range and the bracts did not cover them.  Before these splits, R. canina group ( canina agg.) were the most common rose in Cambridgeshire followed by hybrids with the Northern Dog-rose, despite the fact that Northern Dog-roses do not occur this far south, being limited to north of a line between the Severn Estuary and the Wash. On recent field trips I have found the Northern dog-rose hybrids to be very common but working out what are the parents are is not easy. Hybrids are fertile and backcross.

Hopefully these photos will encourage the purchase of the new rose handbook. It's not perfect but is a major advance. It is photo based and covers a wide range of rose species and hybrids. The increase in the number of hybrids will be quite a challenge.

 Although the conventional wisdom suggests that roses should only be examined in late summer based on the hip being fully formed and sepal position/falling off being critical, I think a lot can be done when roses are in flower. Sepal position changes as the hips ripen and this seems to have very variable timing.

Difficult plants may often require a second visit to aid final identification. 

Finally I have been caught out several times by two different species growing together with intertwined stems which caused confusion, until that was pointed out by someone more expert than I.

Peter Leonard

Cambridgeshire

June 2026

See also, previous blog on Identification of Roses, Leaf Stipules.