Brenton Conifer Research Project

In 2003, the Brenton Arboretum along with Dr. Jeff Iles from the Department of Horticulture at Iowa State University in Ames, Iowa and Dr. Harold Pellet from the Landscape Plant Development Center in Chanhassen, Minnesota have embarked on a observational study involving twelve conifer (cone-bearing plants) species not native to Iowa and typically not being grown in here. Over the course of at least ten years, these twelve conifer species will be continually evaluated to observe how well they are suited for Iowa’s weather extremes, from our hot and dry summers to our cold winters, but more importantly how they will manage our sometimes dry falls and warm winters, when many conifers experience some winter burn.

Over the course of the past four growing seasons, some of these conifers are showing good characteristics, while others have not done so well. Currently, the Korean Fir, Fraser Fir, Japanese Larch, and the Shawnee Brave® Common Baldcypress are the four which have grown the best. The Japanese Larch and the Shawnee Brave® Common Baldcypress both of which are deciduous conifers, meaning they loose there needles in the fall, grew from one to two feet this past year. The Korean Fir and Fraser Fir have not grown as fast, but they repeatedly show minimal to no winter burn.

The Korean Pine, Himalayan White Pine, and the 'Green Giant' Arborvitae are three trees which had not done so well. The small Korean Pines have not become established and will be replaced with new and larger trees to see if they will do better. The Himalayan White Pines continue to die after early dry spring seasons and currently there are none of these pines in the study. The 'Green Giant' Arborvitaes have considerable growth during the summer, but some have died the following spring. A few of these trees remain in the study and we will see how they will perform over the next 12 months.

The Rocky Mountain Firs, Wilson’s Spruce and the Balkan Pines have all been planted in the last two years, and thus they are just starting to become established. The Chinese White Pines are just more established as they had good growth this year, while the Bosnian Pines continue to have slow steady growth, but have shown some winter burn.

Each year, at the end of the growing season, the height and average annual growth of each tree is measured and recorded. Also, at the end of winter, each tree is ranked on a scale of 1-5 according to the degree of winter burn. This data over the course of time will show us how well these trees can survive the Iowa environment.

Fraser Fir, Abies fraseri

Height 30-40ft , Spread 20-25ft, Native to the mountains of West Virginia, North Carolina and Tennessee.

Korean Fir, Abies koreana

Height 15-30ft , Spread 6-12ft, Native to Korea

Rocky Mountain Fir, Abies lasiocarpa

Height 80-100ft, Spread 20-25ft, Native from Alaska to Oregon, Utah and northern New Mexico.

Japanese Larch, Larix kaempferi

Height 70-90ft , Spread 25-40ft, Native to Japan

Wilson’s Spruce, Picea wilsonii

Height 35-60ft , Spread 15-20ft, Native to China

Chinese White Pine, Pinus armandii

Height 30-50ft , Spread 20-30ft, Native to western and central China and Korea

Korean Pine, Pinus koraiensis

Height 30-40ft , Spread 15-20ft, Native to Korea and the mountains of Japan

Bosnian Pine, Pinus leucodermis

Height 30-40ft , Spread 10-20ft, Native to the Balkan Peninsula and southern Italy

Balkan Pine, Pinus peuce

Height 30-60ft , Spread 20-25ft, Native to the Balkans, including limited areas in Albania, Bulgaria, and Greece.

Himalayan White Pine, Pinus wallichiana

Height 30-50ft , Spread 15-30ft, Native from Afghanistan to Nepal

Shawnee Brave® Common Baldcypress, Taxodium distichum 'Mickelson'

Height 50-70ft , Spread 15-20ft, Cultivar selected for its narrow pyramidal habit, Species Native to the eastern United States.

'Green Giant' Arborvitae, Thuja 'Green Giant’

Height 30-40ft , Spread 15-18ft, Cultivar selected for its bright green foliage, Species native from Alaska to northern California and Montana

The Brenton Conifer Research Site Map