Mountain-ash Sorbus americana and S. decora
Family: Rosaceae (Rose)
Branching: Alternate

These small northern trees are not actually Ashes, but members of the Rose family.  There are two native species: American (S. americana) and Showy (S. decora), though they don't seem to be easily separated, especially in the winter.  One introduced species, European (S. aucuparia), is commonly planted in cities, and is the most likely to be found in southern Ontario.  All three closely resemble each other in size and form, especially the two native species.  The main differences are in the buds, which are hairy for European Mountain-ash and shiny and resinous for the native species.  The buds are fairly large, especially the end bud, and are typically reddish in colour.  The bark is usually marked with horizontal slits similar to cherries and birches, though it's not too evident on these pictures..   I'm not sure if any winter characteristics are consistent enough to allow seperation between the two native species...

Winter twig and end bud of a native Mountain-ash

Another view of the end bud and leaf scars

End bud and leaf scars.  Often the leaf scars are crowded together on "spur branches"

Another view of the spur branches with an end bud

Another view of the winter twig.

Young bark

Slightly older bark

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copyright 2008 Josh Sayers
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