Our front yard is home to the most godawful-looking mountain ash on earth. It’s been
pecked by sapsuckers for most of the past 20 years and, aside from a bustle of green
shoots low on the trunk, is either dead or half-dead. Well-intentioned pruning has
only made the situation worse. Why is it still standing? Every time I’m about to reach
for the chainsaw, it comes up with some redeeming feature: bees love the flowers, birds
eat the fruits, the leaves are pretty, the birdfeeders it holds are close to the house. Plus,
a visitor just last week reminded me of the widely held belief that a rowan tree in the
yard brings good luck.
Mountain ashes thrive in the boreal forest’s rocky slopes at high elevations or
bordering cold wetlands. Among goldthread, partridge berry, starflower, and bunchberry
– wherever the song of the white throated sparrow is heard – that’s where mountain
ash is at its best. They’re compact trees, usually 20 feet high or so, and can be lovely,
especially in autumn when yellow leaves complement the bright orange-red of many
clusters of berries. That’s why mountain ash is known as the holly of the north woods.
The pinnately compound leaves have 13 to 17 leaflets, and it is this superficial
similarity to the ashes that led to its name. True ashes are in the olive family and
have opposite compound leaves. The mountain ash is in the rose family; it has alternate leaves with lots more leaflets, and the leaflets have sharply toothed margins.
Technically, the fruits are pomes, not berries, despite the fact that at about three-six-teenths of an inch in diameter, they look more like berries than apples to most of us.
There are well over a hundred species in the genus Sorbus. They grow worldwide in
temperate regions and are most diverse in the mountains of western China. In North
America, they are restricted to cooler regions: eastern Canada and the northeastern
states, plus high in the Appalachians south to Georgia. In yards and gardens, especially
in warmer climes, sapsuckers are not their only problem. This little tree is often short-lived due to fire blight, mildew, and boring insects. They don’t grow well in urban
areas if the air is polluted.
The name rowan was originally given to a
European species but now is used for many other
Sorbuses. Nobody knows exactly how many Sorbus
species exist because its members hybridize freely
and sometimes reproduce without fertilization.
This occurs in other plants, too, and is called
apomixis. It’s when viable seeds are produced
without pollen. Unlike most other plants,
Sorbus species often cross with species in other
genera. The shipova, a Pyrus (pear)-Sorbus cross, for
instance, has been traced back to the early 1600s.
Story by Virginia Barlow
Illustrations by Adelaide Tyrol