2003 Annual and Perennial Trial Results

Garden Glow(TM) A Luminous New Shrub for Northern Gardens

Our industry is faced with several new demographic trends.  Two that figure prominently for breeders of landscape plants are that the size of the average single family building lot is shrinking in size, while the average footprint size for a single family dwelling is growing in size.  As a result, homeowners and landscapers are forced to be more selective in plant choice.  Ideally, each plant should be aesthetically pleasing in multiple seasons.

To an extent, red-stemmed dogwoods (Cornus sericea) are plants that demonstrate such multi-season functionality.  Serving as screens or backdrops to the landscape in the summer months, they jump to the fore in the winter with their vibrant red stems.  The Woody Landscape Plant Breeding project at the University of Minnesota has released two notable red-stemmed dogwoods in the 52 year history of the project.  Isanti and Cardinal released in 1971 and 1986 respectively, are well-known and widely planted in northern landscapes for their extreme cold-hardiness and the color they add to the winter landscape. 

In 2001, the Woody Landscape Plant Breeding project released Garden Glow(TM), tested as UMN970507, a shrub dogwood derived from the species Cornus hessei.  Garden Glow(TM) is a multi-stemmed, shrub that can attain a size of 6 inches x 6 inches in the landscape.  It has a slower growth rate than Cornus sericea and with selective pruning it can easily be managed as a 3-4 inch shrub.  Due to its smaller size and reduced growth rate, Garden Glow(TM) is much better adapted as a residential landscape plant than traditional red-stemmed dogwoods.

Without question the outstanding garden feature of Garden Glow(TM) is the chartreuse, golden yellow summer foliage color (Fig. 1).  For multi-seasonal interest, the plant produces small, attractive flat top cymes of white flowers sporadically through the summer which are followed by rather inconspicuous white to pale blue fruits in the early fall.  Garden Glow(TM) can develop good rosy red to burgundy fall foliage color in the absence of early frosts and red stems and twigs in the winter.

Garden Glow(TM) has been tested for cold hardiness at the University of Minnesota Horticultural Research Center in Excelsior, Minn. both in laboratory freezer tests and in landscape settings.  In controlled laboratory freezer tests, Garden Glow(TM) was hardy to - 47 degrees F.  Based on observations of landscape plantings in Excelsior, Garden Glow(TM) has proven reliably hardy for USDA Plant Hardiness Zone 4a locations.  The plant has also been under observation at the North Central Research and Outreach Center in Grand Rapids, Minn., USDA Plant Hardiness Zone 3b since 2003.

Garden Glow(TM) is adaptable to a range of soil types and will tolerate poorly drained soil conditions.  However, it will thrive in a mulched bed with even soil moisture.  The summer chartreuse, golden yellow foliage color develops best on plants that are grown in morning sun (eastern exposure) or in dappled afternoon sun.  When Garden Glow(TM) is grown in full afternoon sunlight it will suffer burn injury to the foliage in the hottest part of the summer.  Garden Glow(TM) would be an ideal companion plant to hemlocks, rhododendrons, summersweet clethra, hostas, and ligularia species. in a woodland or naturalized garden setting.

Garden Glow(TM) is readily propagated by softwood cuttings treated with 2500 ppm IBA that are stuck and rooted under intermittent mist.  It can also be rooted from hardwood cuttings.  Garden Glow(TM) is being sold under the auspices of the Minnesota Nursery Research Corporation (MNRC), formed in 1957, which collects a voluntary fee for each plant sold to support plant breeding efforts at the University of Minnesota.

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