Green ash trees: leaf arrangement and branching.

Green ash samaras

The female ash trees in the city are positively pregnant with samaras (seed pods) this summer; I haven’t seen them this plump in years.  Green ash (Fraxinus pennsylvanica) are common boulevard trees here in Calgary, hardy souls with excellent drought tolerance.  (Don’t confuse them with Sorbus spp., or mountain ash, which are not the same genus).   Until recently, I had never noticed that ash trees possess opposite branching – that is, each branch has a direct mate on the exact opposite side, except if one of the branches is removed via pruning, mechanical damage, disease, or otherwise.   This feature is a relative rarity:   a few other common trees such as maples and dogwoods have it, but it’s not something you find every day.  Most trees are alternate branching – and so are their leaves.   Ash leaves are composite, with five to nine leaflets – and the leaflets are ordered in an opposite fashion in the same manner as their branches.

So, if my neighbours are wondering what I was doing this afternoon, as I stood under the green ash in the yard, squinting up at the canopy of leaves and branches for what may have been a decidedly odd and mysteriously long time, well, now you know how I “do research”!

DID YOU KNOW?  White or American ash (Fraxinus americana) has been traditionally used to make sports equipment such as baseball bats, cricket bats, hockey sticks…and, my favourite, lacrosse sticks.  If you’re interested, as I am, in the relationship between plants and sports, check out the University of British Columbia’s  excellent “Biodiversity and Sports” archives on their Botany Photo of the Day site:

Lacrosse stick – wood from unknown source


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