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Northern gardeners are always excited to catch wind of new plant introductions they’ll be able to bring into their yards and gardens as the palette of landscape plants gets ever greater. That’s doubly true for plants that have been specifically developed to withstand the rigors of our harsh northern climate.
Over the years, the University of Minnesota has led the way in developing hardy plant varieties for northern yards and gardens, with such renowned releases as the “Lights” series of cold-hardy azaleas, numerous chrysanthemums, roses, apples, grapes, blueberries, and the list goes on.
Thanks to these ongoing breeding efforts at the University, there are some exciting new plant developments on the horizon that are sure to become standards for northerners in the years to come.
You can’t buy them quite yet – many of these new University of Minnesota varieties have passed rigorous tests, but commercial trials and propagation take several years.
After new selections are tested in multiple sites in Minnesota and elsewhere for two to five years, the best performers are sent to commercial trials for virus cleanup, propagation tests, and grower production to meet market standards. Finally, commercial propagation begins, but it can take several years to build up sufficient plant stock for retail nurseries and garden centers.
So as a little teaser, just to keep northern gardeners and landscapers on the edge of their seats, here are a few of the developments you’ll see making their way into the nurseries and garden centers over the next few years.
Breakthroughs in Hardy Perennials
The University’s Mum breeding program is one of the oldest public sector breeding programs in the world and the only one in North America. Developments have led to the highly successful “Minn Mum” series and the recently released “My Favorite” series, whose shrub/cushion plants produce several thousand flowers and are sold worldwide.
University of Minnesota scientists are collecting wild mum species in western China, near Tibet, to add to the germplasm collection. Watch for new colors in shrub-sized cushion mums, including pumpkin, orange, lavender, and purple.
A spreading or “wave” chrysanthemum, only six inches high with a 2- to 3-foot spread, will soon change the way we look at mums, the initial result of a breeding program that will select for varied colors and daisy or double blossoms in the future.
A breakthrough in Easter lilies will be in commercial trials next spring. Frost tolerant, continuously flowering, seed-propagated Easter lilies could dramatically change the cut-flower marketplace where 3- to 4-year-old lily bulbs are grown for one production harvest. These new varieties bloom repeatedly.
A new hardy gaura (Gaura lindheimeri) is in commercial trials. A hardy Minnesota species was crossed with plants gathered on collection trips to Texas, Mexico, California, and the Dakotas, resulting in a fragrant, hardy plant. It could be in retail nurseries as early as 2006.
And in the world of the non-native, a gladiolus hybrid with dwarf species from South Africa shows promising fragrance and hardiness in a plant about 10” high.
Seed propagation makes the plants easier to ship and store, with fewer diseases than the vegetative varieties. University scientists are collecting plants from South Africa to Siberia to develop a wide germplasm pool.
Showy Roses and Azaleas
The “Lights” series of azaleas continues to bring new tropical colors to early spring landscapes across the North. The plants are world-renowned for varied colors and incredible flower bud hardiness – an achievement that initially took two decades.
The first crosses were made in 1957; ‘Northern Lights’, with various shades of fragrant pink flowers on a 4- to 6-foot high bush, was the first introduction.
Since then, 12 new “Lights” have been introduced, including the newly released and highly fragrant ‘Candy Lights’ which features light pink flowers with pale yellow streaks, and ‘Lilac Lights’, with its speckled pinkish-purple flowers.
University azalea breeders are working towards improvements in foliage quality and resistance to powdery mildew. They are also selected for attractive fall foliage color, flower fragrance, and significantly extended bloom periods.
Watch for new colors of red and even maroon flowers and a new series of more compact plants and flowers. Future work will involve screening seedlings collected from 16 species of deciduous azaleas native to the Appalachian Mountains in the eastern United States.
Roses were some of the earliest woody landscape plant cultivars released from the University of Minnesota and a sideline of the chrysanthemum breeding project in the 1940s. The program was reinitiated in 1990 with the goal of developing larger, disease-resistant, hardier shrub roses on their own roots.
Serendipitously, researchers spotted a polyantha rose at the Minnesota Landscape Arboretum that has led to new selections being developed. Several selections of hardy polyantha roses, with their small stature, constant bloom, and large clusters of small flowers, will soon be added to northern landscapes, with several selections scheduled to be released in 2007.
Black spot fungus has challenged gardeners for centuries. Using black spot isolates collected from across eastern North America, University scientists can characterize the molecular diversity of the fungus.
Rose genotypes will be inoculated with these black spot isolates to determine the racial diversity of the isolates. Breeders can then identify black spot resistance genes in rose germplasm and begin the process of incorporating those genes into cold-hardy shrub roses.
Exciting New Tree and Shrub Developments
‘Firefall’ Freeman maple, the newest tree release from the University, is the result of a cross between ‘Beebe’, a cut-leaf silver maple, and an earlier University of Minnesota red maple introduction, ‘Autumn Spire’. Field trials began in 1992, with young trees evaluated for form, cold tolerance, and quality and timing of autumn leaf coloration.
The initial selections were clonally propagated by softwood cuttings in 1994 and distributed to cooperators in Iowa, Oregon, Manitoba, and outstate Minnesota. As a result, this upright tree which has early orange to scarlet fall color was introduced in 2005.
The pagoda dogwood (Cornus alternifolia), also known as alternate leaf dogwood, is native to Minnesota and much of the northern forests. Creamy white blossoms on horizontal branches light up the woods in May and lead to attractive blue fruits in the fall.
Unfortunately, the trees are highly susceptible to Cryptodiaporthe canker, a problem identified more than a century ago. Trees rarely attain a trunk diameter greater than 4” before the tree succumbs.
University of Minnesota researchers collected canker samples from around the state and seeds from hardy trees across Minnesota. Challenging new seedlings with the disease is the first step to breeding a more resistant cultivar. In the process, breeders will select for improved fall color, richer and varied flower color, and larger flower size.
The nannyberry (Viburnum lentago) is a large shrub or small tree with attractive glossy green foliage that turns reddish-purple in fall. Clusters of single white flowers in spring are followed by edible blue fruit in late summer. The species is particularly susceptible to powdery mildew, but University researchers have identified a resistant variety that may be released soon.
A new winter apple, as yet unnamed, will be available for sale in 2006, following three decades of development. Look forward to a rich, sweet flavor with hardiness comparable to “Honeycrisp”.
And there are many more exciting developments in the works at the University of Minnesota, including grapes, blueberries, strawberries, and ornamental and turf grasses – watch for these in the coming years. The excitement has just begun!