Fig. 1. Populus tremula L. f. microphylla C.Hartm. (Finland, Lohja, Karstu, 1960). – Image: Harri Harmaja (scanned from dried specimen). – I have seen this form every now and then in southern Finland. It may somewhat favour rock outcrops as habitat. The dryness does not provoke the species to produce these much reduced leaves as individuals with average leaves may occur side by side. Thus a genetically determined taxon is concerned. – The three morphs presented on this page are examples of leaf size variability in P. tremula (Salicaceae). All images are in the same scale and show leaves in short shoots. Different degrees in the blade of brownish colouration and of silky indumentum are well-known and striking in springtime. The leaves of long shoots are known to be deviating; possibly the short shoots, too, infrequently develop leaves of the former kind.
Fig. 2. Populus tremula (Finland, Espoo, Suvikumpu, 1975). – Image: Harri Harmaja (scanned from dried specimen). – This is a fairly typical representative of the species. However, the leaf blades are rather tall and the petioles rather long in proportion to blade length. I have also elsewhere observed that the relative length of the petiole varies somewhat with trees; attention has hardly been paid to this variability in the literature.
Fig. 3. Populus tremula f. gigas Nilsson-Ehle (Finland, Äänekoski, Pudasjärvi, 1979). – Image: Harri Harmaja (scanned from dried specimen). – This morph is supposedly the well-known triploid with larger leaves. The cordate shape of the latter is also a difference from the diploid main population. A mention of this additional difference, also observed by me in other occurrences of putative triploid aspen trees, has not been detected by me in the literature. This kind of trees formed a stand (apparently a clone) among ubiquitous typical trees. On August 1, 2007 I made a sight record of this taxon in a very famous locality: close to the gate within the estate of Ainola, the home of the notable composer Jean Sibelius (1865-1957).
Created August 18, 2004. Latest revision August 2, 2007.