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Green ash (Fraxinus pensylvanica)

Ash is the “A” in MADCAPHORSE (the memory clue for opposite-leaved woody plants). Ash twigs are moderately thick (about like a pencil), with a true terminal bud.

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Green ash (Fraxinus pensylvanica) terminal bud

In side view, the leaf scars are remote from one another. (Compare to maple, wherein the leaf scars nearly touch one another).

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Green ash (Fraxinus-pensylvanica) lateral buds

Ash is one of those genera where winter characteristics are useful year-round. To distinguish the common upland forest tree white ash (Fraxinus americana) from the very similar low(er)-land species green ash (F. pensylvanica), note how the leaf scars of white ash wrap partly up and around the bud, whereas the leaf scar of green ash has a horizontal top edge, with the bud perched above it.

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White ash (left) and green ash (right) lateral buds

Another twiggily (twiggily?) distinct ash is blue ash, the scientific name of which is very appropriately Fraxinus quadrangulata, meaning “4-angled.” It’s also called “winged ash.”

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Blue, or "winged" ash (Fraxinus quadrangulata) twigs are winged