BY RUSSELL STAFFORD / Berrien Springs, Michigan, Zone 5
HORTICULTURALLY SPEAKING, southeastern Russia—land of the mighty Amur, Earth's sixth-longest river—has much in common with the midwestern United States: a mercurial climate with sweltering summers and bone-chilling winters (the equivalent of USDA Zone 4 or less); a mid-northern latitude; and a fascinating and diverse woodland flora abounding in comely, tenacious plant species. Small wonder, then, that many of the best hardy trees and shrubs for mid-western gardens hail from this kindred place. And great pity that so much of this botanical bounty remains so little known.
Consider, for example, the purpleblow maple (Acer truncatum). Offering a neat, compact habit (25 feet high and wide), chartreuse spring flowers, elephant-gray bark, and dainty leaves that morph from purple in spring to lustrous dark green in summer to dazzling orange yellow in fall, it makes an ideal specimen for small gardens. Yet, ironically, its hybrids ‘Keithsform’ and ‘Warrenred’— both of them taller, coarser, and less beguiling than unadulterated A. truncatum—have usurped its place in the nursery trade. Its somewhat larger sibling, painted maple (A. mono; pictured)—which, in its best forms, combines many of purpleblow maple's virtues with a dramatic, broad-domed, cumulous habit— shares its undeserved obscurity. So, too, do several other outstanding maples of the Amur region, including Manchurian stripebark maple (A. tegmentosum), whose white-veined trunk and bold leaves strike an exotic note in the landscape (particularly in the variety ‘White Tigress’), and Korean maple (A. pseudosieboldianum), a hardier but equally fetching take on Japanese maple (A. palmatum). Like purpleblow and painted maples, these two small (20-25 ft.) species accept any reasonable soil in sun or partial shade.
The Amur woods are also rife with gardenworthy conifers, none more so than Korean pine (Pinus koraiensis). Of somewhat irregular, open habit, with bristling shags of stiff, gray-green needles on gently upswept branches, it is one of those rare and valuable plants that seem to animate the landscape. Although the species can attain 30 to 40 feet in height, several dwarf, blue-needled forms are in cultivation. Lesser than P. koraiensis in size but not in beauty, diversity, or hardiness (Zone 1), dwarf Siberian pine (P. pumila) typically makes a spreading, tufted, densely needled mound one to three feet high, but some forms grow to seven feet or more.
Although taxonomists are thoroughly flummoxed by Amur cork tree (Phellodendron amurense), any gardener who has seen this protean species in its highest incarnations—its sinuous, wide-spreading branches nearly paralleling the ground before rising, candelabra-like, to a flat-topped crown—knows exactly what it is: one of the most picturesque medium-size trees (25-50 feet tall and wide) for northern landscapes. Whether in Russia or Michigan, it is as undemanding as it is ornamental, and requires nothing more than a sunny position.
To do in the garden
- Prune shrubs that bloomed this spring on last year's wood—such as forsythia, weigela, and bridal-wreath spirea.
- To discourage weeds and improve the soil, apply two to three inches of bark or leaf mulch to plantings once the ground has warmed.
- Blanket cucumber, squash, and melon plants with fabric row covers to protect them from cucumber beetles.
Well worth planting both for its femy gray foliage and its early- to midsummer blooms, this woefully under-used and exceptionally hardy (USDA Zone 2) midwestern native is one of the best small shrubs for sunny, dry sites such as rock gardens and embankments. Its flowers tone beautifully with the yellow starburst blooms of hypericums. The three-foot-tall stems die back in winter.