It’s Arbor Month! Across the continent, volunteer tree planters are digging into community tree planting efforts. For many states, trees are celebrated with ceremonial plantings on National Arbor Day, recognized nationwide as the last Friday in April. States have the latitude to declare their own Arbor Days, with the dates varying according to the most favorable local planting conditions.
All 50 states celebrate Arbor Day in some manner, detailed on this Arbor Day Foundation map. Click on your state for a list of Tree City USA® communities, dollars spent on urban forestry management, number of trees planted, per capita investment in each state’s urban forest, and other interesting tree facts. Oregonians celebrate Oregon Arbor Month, with many efforts coordinated by the all-volunteer Oregon Community Trees organization and supported by grants and technical assistance administered by the Oregon Urban and Community Forestry Program.
At the nursery, we’re celebrating Oregon Arbor Month by shipping trees to our customers – and planting trees! We’re finishing up the pruning and potting of several hundred thousand bare root trees for our next container crop. We’re waiting impatiently for the rain to stop and our fields to dry out enough for spring planting.
In recognition of Arbor Day and the importance of trees, we’re featuring BIG TREES in this week’s blog. These large-canopy tree species and cultivars are among our best allies for cooling our fragile, warming planet. They provide cool shade, ecosystem services, and human health benefits in a big way. As essential green infrastructure, large trees provide an array of environmental services including the production of oxygen, filtration of harmful particulates from the air, reduction of urban heat island effect, carbon sequestration, erosion control, reduction of rainfall runoff and much more. Our March 29 blog featured six large canopy oaks: the cultivars Forest Green®, American Dream® Oak and Urban Pinnacle® Oaks, and three species: Red, Bur and Swamp White. Diversify your planting scheme by including these top performing cultivars, representing six Genus and species, in your big tree lineup:
Redmond Linden
Tilia americana ‘Redmond’
Rapid growth and heavy caliper development at a young age give this sturdy cultivar a head start in the nursery and in the landscape. Large leaves give it a bold appearance, casting heavy shade while staying fresh and green through the summer months. Its fragrant yellow flowers that bloom in June attract butterflies and bees and are a source of gourmet honey.
Selected in Nebraska in 1927, this time-tested cultivar of the native North American Basswood has proven over the decades to be hardy through USDA Zone 3. Its adaptability and ease of care makes it among the most widely planted of the linden cultivars. It was named Tree of the Year in 2000 by the Society of Municipal Arborists and a Plant of Merit by the Missouri Botanical Garden in 2009. Find details and photos of this excellent native shade tree on the garden’s Plant Finder.
Green Vase® Zelkova
Zelkova serrata ‘Green Vase’
Small, refined leaves and a distinctive, upright growth habit make Green Vase® Zelkova a great fit for urban streetscapes. Appreciated for its symmetrical vase shaped form, this cultivar has become the standard of comparison for Zelkova serrata cultivars, and a popular choice for designers in search of a look-alike substitute for the classic American elm.
Selected and introduced by Princeton Nurseries of New Jersey in 1985, in an average urban landscape setting, it will grow to an approximate height and spread of 45’ x 30’ in 30 years. Fall color is orange.
Exclamation!® Planetree
Platanus x acerifolia ‘Morton Circle’
The perfect symmetry of this hybrid Planetree demands attention wherever it’s planted. Its upright, pyramidal canopy is shaped by a strong central leader and well-spaced, upright-angled branches. Its resistance to anthracnose and powdery mildew, moderate growth rate, light-fruiting habit and resistance to frost cracking are among reasons to plant this remarkably adaptable urban tree that go far beyond its ease of care and good looks.
A top performer among crosses made in the 1980’s by Dr. George Ware at the Morton Arboretum, Exclamation!® Planetree is a hybrid of an unusually anthracnose-resistant North American native sycamore (P. occidentalis) and the naturally anthracnose-resistant Oriental Planetree (Platanus orientalis).
Triumph™ Elm
Ulmus ‘Morton Glossy’
Appreciated in the nursery for its rapid, yet manageable growth, this hybrid elm is oval in youth and develops a classic American Elm form as it matures to a height and spread of 55’ x 45’. Large, dark green leaves are lustrous through the heat of summer and turn to rich yellow in autumn. Selected at The Morton Arboretum by Dr. George Ware from a controlled cross of Vanguard™ and Accolade™ Elms, it is resistant to Dutch elm disease and elm yellows (phloem necrosis) and is moderately resistant to elm leaf beetle and Japanese beetle.
Flashfire® Maple
Acer saccharum ‘JFS-Caddo2’ PP 23361
Our top pick among trees grown from seed collected from an isolated population of sugar maples in Caddo County, Oklahoma. This strain of heat-adapted sugar maples has evolved in rocky, arid, limestone soils and is therefore better adapted to higher pH soils than is typical of the species. It is also the source of the ‘John Pair’ and ‘Autumn Splendor’ cultivars selected by the late Dr. John Pair of Kansas State University.
Flashfire® Maple is well adapted to hot and dry weather, but still has good cold hardiness. It performs well in colder climates through USDA Zone 4 and also in hotter climates including California and the Southeastern United States, where its bright red fall color is striking and unusual.
Presidential Gold® Ginkgo
Ginkgo biloba ‘The President’
Outstanding in the nursery row and then in the landscape, this robust ginkgo cultivar has great sales appeal in the garden center. Thanks to its strong central leader and full branching at a young age, it is impressive even in the smaller, more portable container sizes preferred by many garden center shoppers . As it matures, it develops a dense upright crown and a broadly pyramidal to oval shape. Fall color of this seedless male selected by Dr. Michael Dirr is bright yellow in the fall.
Typical of the species, it thrives in city growing conditions. In general, ginkgos are tolerant of compacted soils (acid or alkaline) and aren’t bothered much by air pollution, heat or cold, diseases or pests. A bonus feature is resistance to the browsing of deer.
