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Alder is the common name of a genus of over thirty species belonging to the Birch family. Black alder, or Alnus glutinosa, is one of the better choices in the genus. But this tree is popular less for its beauty than its utility, because this is a tree for "problem" areas where few others will grow since Black alder is tolerant of extremes. It is particularly suitable to wet soils, acid or alkaline soils, and cold and exposed locations. It is hardy throughout Europe and, in North America, grows from Ontario almost to the Gulf of Mexico, a vast geographic range. Black alder is reasonably fast-growing, deciduous and typically reaches about 40 to 50 feet. It is pyramidal when young, but becomes more rounded with maturity. The four-inch-wide, dark green, roundish leaves are serrated and pale underneath, which produces a pretty effect when stirred by a breeze. But it’s the fruits which are the most interesting; small, cone-like, and persisting through winter, long after the darkening leaves have fallen. These fruits, a boon to foraging wildlife, along with the attractively furrowed bark, make even the ordinary Black alder an attractive winter subject.

But the good news is that there are cultivars available that possess all of the tough, low maintenance adaptability of the Black alder with some spectacular special effects. And one of these "must-have" varieties is Imperial Black alder or Alnus glutinosa 'Imperialis'. This is a graceful, slender tree with mid-green, pinnate leaves and pale-purple flowers in winter. Attractive, almost willowy, this tree offers some of the most attractive leaves of any tree. They are similar to some Japanese maples with their long filigree-like, highly dissected foliage. The elegance of the foliage combined with the slender, pyramidal-form makes a lovely ornamental from an otherwise utilitarian tree. Imperial Black alder has even earned an Award of Garden Merit from the Royal Horticultural Society.
There are other exceptional cultivars as well, some of which are:

'Aurea' - Leaves emerge strong yellow.

'Laciniata' - This cultivar has shallowly-dissected leaves.

'Pyramidalis' (or 'Fastigiata') – is a tree which grows upright.

As usual, trees this special will not be found in the popular landscape nurseries but more likely in a specialty, mail-order, plant nursery.

Imperial Black alder