|G. dissectum 5th Feb 2020|
Despite the leaf shape changing on certain species like G. dissectum, the petiole (leaf stalk) hairs still provide a reliable method of separating the geraniums. A slight complication is that winter leaf stalks can have fewer hairs. I did find a G. pusillium petiole which had no hairs but fortunately later leaves on the same plant had the normal hairs.
1) G. molle ( Dove's-foot Crane's-bill) vs G. pyrenaicum ( Hedgerow Crane's-bill)
These two species share the three types of leaf stalk hairs, short glandular hairs , short simple hairs and long hairs. The difference is that the G. molle long hairs are wispy and are even longer than G. pyrenacium.
|G. molle showing wispy long hairs. Rampton 24th March 2020|
|G. molle showing the short glandular hairs , the simple hairs and the long wispy hairs.|
|G. pyrenaicum showing three types of hair, short glandular, short simple hairs and long hairs.|
|G. pyrenaicum showing detail of the three types of hairs. Landbeach 24th March 2020|
Some of the hairs are angled but this is not Cut-leaved which does not have the long hairs. See below.
Variation and similarity of the three basic hair types makes this quite difficult. The density of long hairs can vary with some G.molle having a dense layer of these wispy long hairs while other plants may have much fewer. The Landbeach photo above is slightly odd in that the long hairs are very dense and downward pointing which gets close to the appearance of G. dissectum ( Cut-leaved Crane's-bill). The following photo which shows the same leaf and stem which gives a less detailed view showing that overall the hairs are not as downward pointing as you might expect in G. dissectum. This plus the leaf shape confirmed identity as G. pyrenaicum ( Hedgerow Crane's-bill). Hedgerow Crane's-bill is often a much more robust plant that G. Molle with bigger leaves.
|G. pyrenaicum. Landbeach|
|G. pyrenaicum leaf|
|G. dissectum winter leaf, Rampton 24th March|
|G. dissectum 5th Feb 2020|
|G. dissectum leaf showing trend towards summer leaves.|
|G.dissectum Leaf showing more deeply cut sections. Rampton 24th March 2020|
Whether the more compact leaf shape is more frost resistant comes to mind.
Petiole (Leaf Stem) hairs.
|G. dissectum hairs showing short glandular hairs and angled straight hairs.|
|G. dissectum, less hairy stem. Angled hairs.|
Key feature is the straight eglandular hairs are angled downwards at up to 45 degrees. The short glandular hairs are just visible in the top photo. The extremely long hairs that G. molle/G. pyrenaicum show are not present.
3) G. pusillum ( Small-flowered Crane's-bill)
|G. pusillum leaf hairs, short glandular hairs plus short glandular hairs. No long hairs.|
|G. pusillum Devils Ditch, 25th March 2020|
Some winter/early spring petioles (leaf stems) have almost no hairs. Normally they have a few short glandular hairs and lots of simple hairs that can be straight or curved. Because the short hairs tend to be all the same length and quite dense they make up a consistent layer.
Whereas leaf shape is variable, the hairs on the petiole ( leaf stem) do seem to give a consistent method of identification provided you have not found a garden escape which would make the situation much more complicated.
Peter G. Leonard
30th March 2020