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Thursday, August 18, 2016



Thursday, 7:45 AM.  69 degrees F at the ferry dock, 66 on the back porch. Wind WSW, calm with light gusts.  The sky is clear, the humidity 86%.  The barometer is falling precipitously, now at 29.95", predicting a chance of thunderstorms tomorrow and rain on Saturday, then clearing and cooler Sunday through midweek.  Rain would be welcome, as long as I get the lawn mowed this morning.
   Another sign that summer is waning is the ripening of mountain ash berries.  Mountain ash, small trees in the genus  Sorbus in the Rose Family and closely related to apples and pears, are of course not ash species at all, as ash are in the genus Fraxinus which is in the Olive Family.  The common name Mountain ash relates to its feather compound leaf, which is ash-like in appearance.  The two tree genera bear no other similarity, and scientific nomenclature of plants is based upon flower structure and its evolution.
   The mountain ash species most likely to be encountered are very similar in appearance and use, the most popular being the European mountain ash, Sorbus aucuparia, and the American mountain ash, Sorbus americana.  I find them very difficult to tell apart (although the winter buds of americana tend to be sticky), and the Europoean species is very much naturalized and commonly found growing as a volunteer in the wild around human habitation. For landscape purposes the two species are very comparable, even the orange, edible berries being very similar.  In recent years the most popular mountain ash sold by nurseries is the also-native showy mountain ash, Sorbus decora, which has berries that are red rather than orange.  The Korean mountain ash is sometimes available in nurseries, and is also a very handsome tree.  The European mountain ash has long been called the rowan tree in Europe.
   Mountain ash trees have great landscape value, as they are beautiful in flower and in fruit, and provide great wildlife food.  Many individual mountain ash also have good fall leaf color, and some northern countries brew a beer from the berries.  Mountain ash are all small trees or multi-stemmed large shrubs of the far north, the North American species being trees of the Boreal Forest biome.
   Sorbus species do have some problems, one being fire blight, which is also a very common disease of apples, pears and quince.  Sap suckers, which are small woodpeckers, can be very destructive, drilling holes in the soft bark in order to drink the flowing sap in the spring.  They can girdle and kill trees they take a liking to.
   Knowing the difference between mountain ash (Sorbus) and true ash trees (Fraxinus) is very important when dealing with Emerald Ash Borer, as that pest only attacks Fraxinus species. 

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