The leaf shapes are shown below:
 |
| upperside of "typical" leaf |
 |
| Underside of a different "typical leaf" |
You can see the overall almost triangular shapes, the flat bases and the slightly acuminate tips. On the upperside view at the base of the blade you can see hints of the glands at the top of the petiole (reddish?) and if you expand the photos by clicking on them, and look at the margins you can see the toothed serrations on the "transparent" margin, rather like breaking waves on a shore. Download the pictures for a more detailed look at these finer points. The bilaterally flattened petioles that encourage the leaves to tremble (not as much as an aspen though) are also fairly clear, lying over on one side or the other. From the ground the leaves are obviously large, and show somewhat matt greyish from below, certainly in comparison to the other supposed 'Italica' windbreaks in the immediate area, which generally have leaves only about one fifth the area of one of these!
Its difficult to be sure, but this may not be one of the classic fastigiate poplars (the windbreak has only recently been pollarded and is in its first couple of years of regrowth, and I just can't remember the original shape of the trees. If so, it may be 'Robusta' a more rounded spire shaped form of the "black poplar hybrid" trees, very commonly planted in windbreaks nowadays according to the Collins guide. There are a number of others to choose from, but this is stated to be a hybrid between P. nigra 'Plantierensis' and P. deltoides 'Cordata', so a touch of the American in its ancestry, which as in many of these black poplar hybrid crosses is actually quite dominant! This particular cultivar, if 'Robusta' is what this tree actually is, arose in France in 1895, indicating a cross with only 10 year old trees of 'Plantierensis', quite a significant act of faith perhaps ! There are however quite a few other common cultivars in this hybrid US x European group, sometimes known generically as P x euramericana, to choose from, all of which grow very rapidly as all hybrid stock should - from applied genetic theory, just right for growing matchsticks or creating windbreaks!
The shoots are stout (fully 6 mm diameter) olive yellowish green on this year's growth , held quite upright, with whitish lenticals about 2 mm long and 1 mm wide, right to the growth tip, which is still going strong. The younger half of the shoot is quite furrowed or rather ribbed with long buttresses to the leaf petioles. There are clear longish narrow buds about 9 mm long at present, with some droplets of brownish exuded liquor, and some brownish colour to the scales.
The leaves are mid-green, glossier above, at the moment, with light green flattened petioles. Rotating the twig shows how these flutter from one side to the other! There is generally a pair of minor basal veins, sometimes almost ruler straight just above the base of the leaf, not clearly upcurved (and branching primarily below) towards the tip as the main vein branches are. The veins show paler against the mid-green background of the lamina and they are the same colour as the petioles. Any pubescence is now (mid-August) well gone, together with the stipules, of which there is little sign except for the paired minor brown scarring, to one side and the other of the axillary bud, right down to the half-expanded young leaves where they are apparently represented by small green triangular structures. Each petiole carries a "triple buttress" ribbing, even quite low down the shoot.
A solitary light brown thrips nymph was noted patrolling close to the petiole-lamina junction on the upperside of the lamina. Various small differently shaped holes (possible capsid?) and feeding specks were also seen.
No comments:
Post a Comment