By Tracy Ilene Miller
Wilsonville, OR (November 1, 2006)- Customers are always requesting that growers sell new and different trees are. The process of evaluating a tree’s viability as part of the product mix can take years, however, and once added to the inventory, it’s a guessing game how many to maintain in stock from year to year. But, in a general sense, growers are betting on trees that are smaller, have a narrower or more upright growth habit and display attractive features in more than one season. Multi-seasonal interest brings additional value to some varieties that are meeting the needs of customers looking for trees to fit on smaller lots.
Cercis (redbud) species overall have become more popular not only because of their size but also for their ability to perform year-round. A favorite of Steve Dukes, production manager of EF Nursery Inc. in Forest Grove, Ore., is Cercis canadensis ‘Forest Pansy.’
“The foliage is tremendous,” says Dukes, adding that the bloom that arrives before it leafs out is a striking rosy-burgundy. The blooms are clusters of color along the branches and trunks and are followed by leaves that open bright purple before they settle into a deeper tone with green highlights. The pods and the colorful fall display round out the attractiveness on the 20-foot tree.
EF Nursery grows ‘Forest Pansy’ using tissue culture as part of its bare-root program. The trees are grown on their own roots, so if the new, small plantings are subjected to freeze damage, the true variety will return. Dukes says because Cercis is doing well, the nursery has just added C. canadensis ‘Lavender Twist’ to its specimen program. The unique, weeping form produces deep lilac blooms up and down arching branches. The vigorous tree usually tops out at about 7 feet and produces blue-green foliage that turns yellow-bronze in fall.
Jim Larson, general manager of Cascadian Nurseries Inc. in Hillsboro, Ore., weighs in with another Cercis – C. siliquastrum (Judas tree) – as one of his favorites. It grows slowly, in about 8-10 years, to its mature height of 25 feet, while maintaining an attractive, delicate look. The reddish-pink flowers come out in late winter to early spring, followed by purplish red seeds that last from late summer into fall. The veins of the glossy, heart-shaped leaves maintain the same purple-burgundy hue of the bark. (As a bit of trivia: The plant supposedly earned its distinctive name based on the legend that Judas hanged himself from this species of tree after revealing Christ.)
Cercis has its pods that hold on, but there are a few trees with fruit – some actually edible, others edible in theory – that add that summer-color element to some high-performing trees. For instance, Cornus mas (cornelian cherry) has three-quarter-inch edible fruit that can last from early spring into fall (if the birds don’t eat them, says Larson), and then there are the small, yellow inflorescences in late winter, which provide an impressive show on bare stems. Cornelian cherry often stays small enough to be referred to as a large shrub rather than a small tree, but it can reach maturity at 15 feet tall by 20 feet wide.
Berries are what will appear after the dazzling white flowers of Amelanchier x grandiflora ‘Autumn Brilliance’ appear in very early spring, with the berries turning on their show with changes from green to red to purplish-black through early summer. If the birds don’t get them, the berries of this serviceberry are delectable and used like blueberries or blackberries in recipes.
‘Autumn Brilliance’ is a new tree to grow at Oregon Turf and Tree Farms in Hubbard, Ore., says tree manager Chuck DeJardin, where two new Amelanchier were added for their versatility, hardiness, showiness and small shape. And ‘Autumn Brilliance’ may have the berries, but it also has a fabulous fall display that earns it its name – red and orange tones with a hint of yellow. Amelanchier canadensis ‘Glenn Form’ Rainbow Pillar is the other new serviceberry DeJardin added. ‘Rainbow Pillar’ has the white flowers distinctive to a serviceberry, but it goes through a spectrum of fall color on a particularly upright form that can be used successfully as an attractive hedge. Both Amelanchier mature at about 20 feet high, DeJardin says.
Then there are the cultivars of trees with multi-seasonal interest and fruit that, in theory, should be edible but really are usually left for the birds are falling into this category. Many Crataegus, with their tolerance for a range of growing conditions, a natural small and oval shape and year-round interest. Crataegus x lavelleei (hawthorn) is one of DeJardin’s favorites, because distinct orange berries hang on nearly all winter, while other Crataegus drop their berries much sooner.
At EF Nursery, Dukes says Crataegus crus-galli is attractive for its “super-high gloss leaf,” masses of white flowers, red berries, great fall display and exfoliating bark. “We grow a lot of other hawthorns,” Dukes says. “We are selling out of 2-inch (caliper) as fast as we can grow them.” White flowers are also the hallmark of an all-around favorite of multi-seasonal trees, Styrax japonicus (Japanese snowbell). Larson has always liked the white, bell-shaped flowers that continue their attractive display of hanging drupes into summer and fall. The tree maintains a small, rounded shape, which makes it tops on many city lists of acceptable street trees.
EF Nursery grows multi- and single-stem forms of Japanese snowbell in greenhouses for a few years, because they do better planted first in containers before they are taken out to be finished as field-grown trees, Dukes says.
For a larger display, Magnolia grandiflora ‘Victoria’ shows fabulous blooms before it leafs out. For its hardiness, it earned the Royal Horticultural Society Award of Garden Merit in 2002. It blooms during winter and all year, with high-gloss green leaves surrounding the soft-white blooms. Overall, Dukes prefers magnolia over Ginkgo, which also are sellout trees, because the growing losses are much less, and there are almost no problems with disease or insects with Magnolia.
“We were doing 250 per year, and now we’re up to 500 per year, and we may even go higher than that,” Dukes says. Syringa pekinensis ‘Morton’ China Snow (Peking lilac) is a tree in limited release from Chicagoland Grows. DeJardin is just starting to grow it at Oregon Turf and Tree Farms, but he says he will need a few years to evaluate it. Nonetheless, it looks promising for its fragrant, white flowers in early summer and an amber-colored, exfoliating bark that appears below the upright, medium-size tree’s leaf line.
At EF Nursery, Dukes likes to prune Acer griseum (paperbark maple) himself to develop its shape. Considered one of the most attractive maples, these showy trees sell out as fast as Dukes can grow them. When he found 50 “hiding” between rows of other trees, he sold them all within 10 days. “I’m trying to get my numbers up, to about 500 on that variety, to get to 2.5- and 3-inch,” Dukes says. “Anywhere it is hard to find 3 inches.”
Even small branches will display the exfoliating bark that ranges in color from cinnamon to orange to contrast against the late-fall display of bright orange-red leaves. At Oakview Nursery Inc. in Salem, Ore., co-owner Pam Dauenhauer is growing Cercidiphyllum japonicum (katsura tree) because of increased requests. The delicate, heart-shaped leaves emerge reddish-purple in spring; they turn blue-green in summer, then yellow to apricot in fall. Mature trees, at about 40 feet, have some bark peeling and a strong, spicy fragrance just before leaf drop.
Ginkgo biloba ‘Fastigiata’ (columnar ginkgo) is on the list of recommended trees for some cities due to its slow-growing, pyramidal shape. The two-lobed leaves, which resemble maidenhair fern, go through a dazzling display of golden-yellow color, albeit short-lived. Growing taller than most other cultivars mentioned here, male trees (without the annoying fruits of female) are nonetheless graceful and fast-selling trees.
Koelreuteria paniculata ‘Fastigiata’ (columnar golden rain tree), grown at Cascadian Nurseries, matures to as tall as 25 feet but maintains a compact 4- to 6-foot spread, making it a much-approved city tree. The compound leaves show golden in the fall, and more gold – in the form of yellow flower panicles – appears in spring, followed by seed pods that go through their own color change.
EF Nursery sells a lot more Pyrus calleryana ‘Cleveland Select’ than P. calleryana ‘Capital,’ but the latter is one Dukes says he would pick for his yard, mainly because of the high-glo
ss leaf, fewer insect and disease problems when compared with other pear cultivars and the ease of growth. The leaves turn reddish-purple in fall, and clusters of white flowers appear in spring on the fast- and tight-growing 30- to 40-foot column. “It has a lot going for it,” Dukes says. Growers are learning that raising trees that have a lot going for them usually means a lot is going into the bank.