Geranium in early spring.

Following on from my ID Key on Geraniums and Stork's-bills which was aimed at flowering plants, I have found identification in winter/early spring, introduces the extra complication of winter leaf shape in Cut-leaved Crane's-bill ( G. dissectum) which looks much like G. molle, G. pusillum and G. pyrenaicum. These four species are covered in the following photos.

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.

The long hairs which tend to be angled down on G. pyrenaicum are not wispy but stronger and less bendy.

G. pyrenaicum showing detail of the three types of hairs. Landbeach 24th March 2020
Some of the hairs are angled up to 45 degrees . 

Hedgerow Cranesbill when in flower have flower stems without the long hairs.

G. pyrenaicum flower stalk with no long hairs.

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

2) G. dissectum Cut-leaved Crane's-bill.

G. dissectum winter leaf, Rampton 24th March

First problem is that the winter leaves are not the thin cut versions of summer but rather like the G. molle/G. pusillum/G. pyrenaicum cut to 2/3rds type. Later leaves tend towards the thinner cut leaves as spring passes.

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

I will let others think about what the advantage of changing the leaf shape from winter to summer is.
Whether the more compact leaf shape is more frost resistant comes to mind.


Petiole (Leaf Stem) hairs.
Not easy to separate from G. pyrenaicum because dissectum can vary from sparse to dense hairs. G. dissectum can sometimes have very few glandular hairs but these are often quite dense just below the leaf. 

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.

Conclusion.
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
Rampton
Cambridgeshire.
30th March 2020