The NC-7 Regional Woody Ornamental Trials is a collaborative effort between the U.S. Department of Agriculture and state agricultural experiment stations in the Midwest. The goal of this project is to identify trees and shrubs for the nursery trade that will perform well in home landscapes. Paul Ovrom of the USDA’s North Central Regional Plant Introduction Station in Ames, Iowa, and one of the coordinators of the NC-7 trials, compiled the following report exclusively for Organic Gardening on 10 winners that are now available at nurseries in the United States and Canada
Top Shrubs you can Plants
1. Fragrant Sumac ‘Konza’
USDA hardiness zones: 5 to 9
Fragrant Sumac Rhus aromatica is native to much of the eastern United States and southeastern Canada. ‘Konza’ is a deciduous variety of fragrant sumac that grows to about 9 feet tall, fruits heavily, and has dark red foliage in fall. Use ‘Konza’ in borders or hedges, or as foundation plants. In the trials, ‘Konza’ has adapted well to a wide variety of climates and soil types, and has been particularly drought tolerant. Fully hardy in USDA zones 5 to 9, ‘Konza suffered winter twig injury in the trials in USDA zones 3 and 4.
2. Silver Buffaloberry ‘Sakakawea’
Hardiness zones: 2 to 6
Silver Buffaloberry (Shepherdia argentea) is native to the North American plains from Manitoba to Kansas and Nevada. It’s a large shrub (up to 20 feet tall) with silvery leaves, similar in appearance to Russian olive. Its fruits are red to orange-red. Use it for windbreaks, hedges, and specimens. It grows well in poor, alkaline soils and dry conditions, as well as infertile soils and those with lower (more acidic) pH.
Developed at the USDA’s Bismarck, ND Plant Materials Center, ‘Sakakawea’ should perform well in the central regions of the United States and, if planted in well-drained soil, in other areas of the United States and southern Canada from USDA zones 2b to 6b.
3. Red Osier Dogwood ‘Cardinal’
Hardiness zones: 3 to 5
Red Osier Dogwood (Comus sericea), which grows up to 10 feet tall and to 12 feet wide, is found from Newfoundland to Manitoba and on to the Pacific Northwest, and south to Virginia and New Mexico. Researchers at the University of Minnesota shrub-breeding program selected ‘Cardinal’ for its bright, cherry red twig color, which is a stand-out in the winter landscape. Its leaves also turn bright red in fall. ‘Cardinal’ has the most dramatic visual impact when planted as massings and screens, but the plants can also be used individually.
As you might expect from a plant bred in Minnesota, ‘Cardinal’ is very winter hardy and performs well throughout the eastern U.S. and southeastern Canada. It also fares well in western North America where moisture is adequate.
4. Silky Dogwood ‘Indigo’
Hardiness zones: 4 to 9
Silky Dogwood (Comus amomum) is a native shrub of eastern and north-central United States and southeastern and south-central Canada. ‘Indigo’, selected at the NRCS Rose Lake Plant Materials Center, East Lansing, Michigan, is a dense, multi-stemmed shrub that can grow to 10 feet tall. The stems are red when young but turn brown and gray as they mature. Yellowish-white flowers bloom in mid-June. Abundant fruit is often produced, and the fruit ripens in September. The fruit is pale to dark blue and about a quarter-inch in diameter. ‘Indigo’ is adapted to a wide range of soils and grows from somewhat poorly drained to well-drained sites. It has shown slight leaf chlorosis in alkaline soil. It is moderately shade tolerant, but not drought tolerant.
5. Ninebark ‘Nugget’
Hardiness zones: 3 to 6
Ninebark (Physocarpus opulifolius) is a popular shrub native to northeastern and north-central United States and southeastern and south-central Canada. ‘Nugget’ is a fine-textured, compact (5 feet by 3 feet) plant with lime-green colored leaves. Its clusters of small whitish flowers open in early summer. ‘Nugget’ is best used in borders, massings, and hedges.
6. Viburnum ‘Emerald Triumph’
Hardiness zones: 3 to 7
Viburnum ‘Emerald Triumph’ is a cross of Viburnum burejaeticum and Viburnum ‘Allegheny’. It has a compact habit—10 feet high and wide—glossy, dark green foliage and white, nearly flat clusters of flowers in late spring. Its fruit begins to turn bright red in early August and gradually turning black by mid-autumn. South of USDA zone 4, the fall color is bronze to dark red. Above zone 5, the fall color may not have time to develop prior to the first hard freeze of autumn. ‘Emerald Triumph’ should perform well throughout the eastern half of the United States, the west coast, and in the Great Plains and Basin areas with adequate moisture and protection.
7. Barberry ‘Emerald Carousel’
Hardiness zones: 3 to 8
‘Emerald Carousel’ barberry (Berberis koreana x thunbergii) is an attractive hybrid between two widely grown barberries. In spring, its foliage is yellow edged in red, then it darkens to bright green as the season progresses. Small golden-yellow flowers hang in clusters from the arching branches in mid-spring. ‘Emerald Carousel’ bears clusters of eye-catching red fruits. It grows to about 3 feet tall. ‘Emerald Carousel’ should be adapted to most of the eastern half of the United States and throughout much of the West with adequate moisture.
8. Weigela ‘White Knight’
Hardiness zones: 3 to 8
‘White Knight’ Weigela (Weigela florida) is the product of crossing two unpatented weigela varieties. Its winter hardiness and mild fragrance distinguish it from all other common, white-flowered Weigela. Its flowers are funnel-shaped, borne the length of upright stems, and begin as pinkish-white buds opening, in USDA zone 5, to pure white flowers in late May or early June. Its foliage is medium green and virtually free of insects and diseases. ‘White Knight’ can withstand judicious pruning to alleviate any unsightly appearance after a rigorous winter. Use ‘White Knight’ for hedging, massing, or as an accent around building foundations. It typically reaches about 5 feet tall and 6 feet wide.
Choosing the Trees
9. Western Larch
Hardiness zones: 4 to 7
Western larch (Larix occidentalis) is native to the higher elevations of western Montana, northern Idaho, eastern portions of Washington and Oregon, and southeastern British Columbia. One of the tallest species of larch, it reaches up to 150 feet tall. Typical of larch species, this deciduous conifer drops its leaves in the fall. The needles turn a bright yellow before they drop. The spring growth of new needles is also very attractive. The tree has a nice pyramidal form, but should only be used in areas that can accommodate its wide branching habit. Western larch is adapted to wet or well-drained sites and can tolerate a wide range of soil pH. It should perform well in much of the United States and southern Canada.
10. River Birch ‘Little King’
Hardiness zones: 4 to 7
‘Little King’ River Birch (Betula nigra) is an unusual cultivar of the commonly used River Birch tree. The unusual species is native to the eastern United States west to Minnesota and Kansas and can be found as far south as Florida. ‘Little King’ is a low-branched, small tree that grows only 7 to 8 feet in a 10-year period. The tree has a pronounced, rounded-pyramidal habit. Early spring foliage is bright green, the slightly darker summer foliage is glossy. The exfoliating (peeling) bark is broken into patterns of pale salmon and shades of cinnamon-red. ‘Little King’ has excellent resistance to borers, chlorosis, and heat stress. The neat, compact habit of this cultivar should make it ideal for use as specimen plants, borders, low maintenance landscapes, and hedges. ‘Little King’ will perform well throughout the eastern United States and adjoining southern Canada, the Midwest, protected areas in the Great Plains, and throughout much of the West with adequate moisture.
Tree Planting Season
Fall is the second planting season of the year. After enduring a summer with insufficient shade you may be thinking of planting a tree. The first decision is to choose a tree that is suitable for the local climate.
Eric Seaborn, Program Coordinator of the Urban and Community Forestry Program which operates under the Department of Conservation and Recreation here in Massachusetts gave me advice about tree planting. He said the biggest mistake people make is planting the tree too deeply. He says if you buy a tree with a wrapped root ball it is essential to tear away the burlap and remove any wiring, as well as some of the soil to find the root flare and plant the tree at that depth.
If the soil is really poor enrich the removed soil with compost as you replace it. Water deeply and keep it watered throughout its first year.
Staking a newly planted tree is advisable, especially if the location is windy. Two or three firm stakes will do the job. Never use wire that will cut into the tender bark. One common method is to thread the wire through lengths of hose. Make sure to allow for some movement of the tree. Stakes should be removed after one year.
Finally, the tree can be mulched. Mulch should not be deep. Two to four inches is sufficient. Mulch controls weeds, conserves moisture, provides nutrients to the soil as it breaks down, and protects the tree from damage by lawnmowers and string trimmers. Mounding deep mulch up around the trunk is a danger to the tree’s health. It will suffocate surface roots, reduce infiltration of water, and makes a happy home for rodents who will feed on the outer bark and kill the tree.
“When the trunk is buried under a ‘mulch volcano’ it may send out shoots or even fine roots that are of no use to the tree. The roots and the collar of the tree are its most sensitive areas, yet people pay little attention to them,” Seaborn said.
Landscapers Can Also Make Errors
If you use a landscaper watch his practices. Mulch should never touch the tree trunk. It should be spread out around the tree, not up to the tree, and never touch the tree.
Control of Tree Seedlings in Lawns
Many trees such as female ash, Siberian elm, honeylocust, hawthorn, crabapple, maple, and golden rain tree may seed themselves in lawns. Dense turf and mowing to a 3-inch height should inhibit most tree seedlings. Lawns thinned from shade or poor cultural practices are more susceptible to weed invasion, including unwanted tree seedlings.
Aerate, fertilize and properly water the lawn to thicken it and make it more difficult for tree seedlings and other weeds to establish. Some pre-emergents such as pendimethalin do a good job of preventing broadleaf and grass emergence and may control unwanted tree seedlings.
Trees such as aspen, sumac, plum, and Schubert chokecherry may appear as though they reseed themselves in the lawn. Instead, these species produce suckers, which are shoots arising from the lower stem or roots of the tree. They should not be confused with seedlings, which form from seeds.