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Plant Highlight: Eucalyptus polyanthemos

A really big tree

February 2012

Eucalyptus polyanthemos is known in Australia as Red Box (in reference to its reddish wood, used for various purposes including fence posts and railroad ties).  It grows to be a good-sized tree, with a height of about 30 to 75 feet (10 to 23 m).  In California, it is known as the Silver Dollar Gum, with “gum” being a term for eucalyptus, and the “silver dollar” referring to its round grayish juvenile leaves.  These attractive pallid leaves lose their round shape as the tree matures, becoming oval-pointed.  Because the round leaves of the immature tree are prized for use in flower arranging, some growers continually cut down the plants in order to get new sprouts with new crops of juvenile leaves.

The trunk of Eucalyptus polyanthemos is initially shaggy-barked.  In some forms, this rough outer bark is shed to reveal a smoother mottled under-bark, but in other specimens the bark remains shaggy.  The grayish blue-green A leave with flowers blooming all around itleaves are a major part of the tree’s appeal.  The round young leaves are about 2 to 3 inches across (50 to 75 mm), while the mature leaves are lanceolate (shaped like the head of a lance) and about 2½ to 4 inches long (60 to 100 mm).

Eucalyptus polyanthemos comes from southeastern Australia, and it flowers there mainly in spring to summer.  However, our trees at The Ruth Bancroft Garden consistently flower in winter.  The tiny buds are produced in clusters, A close up of a flowerand look like miniature powdery-white upside-down Hershey’s Kisses, topped with a little dome-like cap.  The cap is flushed with a purplish-red color, but it soon pops off to expose the cluster of white stamens within.  The stamens expand to reveal a yellowish center.  Even fully expanded, the flowers are only a little over ⅓ inch across (10 mm).

After the stamens have gone by, the base of the flower becomes a woody capsule, losing its coating of white powder and looking like a miniature reddish or brown Chianti bottle.