The European mountain-ash (Sorbus aucuparia) is a desirable tree for giving variety of expression on the outer edge of groups, and the same is true of the American species (Sorbus Americana). The latter, as obtained from the upper lake region, is a round-topped handsome small tree that loads with bright-colored fruits, even more freely than the European. It is also much hardier than the foreign species in the Northwest.
The oak-leaved mountain-ash (Sorbus quercifolia), Fig. 92, is more regular in form and for certain positions is more ornamental than either of the above, but is not so hardy as the American species. The white beam tree (Pyrus aria) of west and east Europe is closely related to the mountain-ash and crosses readily with it. Its foliage is broad and distinct, and some of its varieties are hardy in all parts of the Union. The varieties argentea and alpestris, from east Europe and central Asia, are hardy far north, and will, when better known, be much used in ornamental planting.
Fig. 92. - Oak-leaved mountain-ash (Pyrus aucuparia quercifolia) (After Maynard.)