Picea abies 'Swanson's Unknown' / Swanson's Unknown Norway spruce

Picea abies 'Swanson's Unknown' is a a flat, spreading form of Norway spruce with uniform, layered branches and medium green needles. It is similar in structure to Picea abies 'Pumila' but has much lighter green needles and a tendency to mound up in the center with age. After 10 years of growth, a mature specimen will measure 18 inches (45 cm) tall and 4.5 feet (1.5 m) wide, an annual growth rate of 4 to 6 inches (20 - 30 cm).

This cultivar orginated as a seedling selected in 1987 at Swanson Brothers Nursery, formerly somewhere in the eastern U.S. Joe Stupka, Pulaski, Pennsylvania reintroduced it after the death of the Swanson brothers and closing of the nursery. A mature plant currently lives in Bickhaupt arboretum, Clinton, Iowa and it is doubtful that many other other examples exist elsewhere. Welch and Haddow list the plant in The World Checklist of Conifers with the comment that 'Swanson's Unknown' is an "unsatisfactory cultivar name."

Picea abies 'Swanson's Unknown' — a mature plant at Bickelhaupt Arboretum, Clinton, Iowa; possibly one of the only known examples.
Photo by Dax Herbst