Columnar Trees

Indiscriminately planting a tree without considering its growth habit and ultimate size can lead to detrimental problems years down the road. Many homeowners want to plant trees next to their house or yard for the shade, privacy, or aesthetic appeal they provide but permanent buildings, property lines, and nearby power lines limit the possible choices. One of the most interesting and useful growth habits for locations such as these is the fastigiate or columnar growth form. Though fastigiate (10:1) and columnar (5:1) differ slightly in height to width ratios, they are variations of a similar theme; their narrow and upright growth habit is accompanied by the ability of their side branches to extend vertically for better light absorption.

Columnar trees are best used in one of two ways – either grouped in multiples for a vertical screen or as a specimen plant for architectural interest. Because of their narrow growth habit, groupings of columnar trees are planted closer together. When planted in a row, the minimum length of the planting is recommended to be around 1.5 the mature height of the tree itself. Therefore, a columnar tree maturing to a height of 40 feet would need a 60-foot run of trees. As a specimen plant, columnar trees can provide a focal point to the landscape, in addition to providing shade around foundation beds, entryway gardens, or island plantings.

The Arboretum established the Columnar Tree collection in 2017 with the planting of two memorial trees for Ruby and Griffith Buck, longtime Arboretum supporters. A ‘Regal Prince’ oak, a hybrid between Quercus bicolor and Quercus robur ‘Fastigiata’ was planted for Ruby Buck. An  ‘Armstrong’ maple, Acer X fremontii ‘Armstrong’, honors Dr. Griffith Buck, hybridizer of hardy shrub roses at Iowa State University. In 2019, a beech, Fagus sylvaticus ‘Darwyk Gold’, was planted in memory of Harry Nichols, another member of the Department of Horticulture at ISU. Other trees in the collection were damaged by the August 2020 derecho but plans are being made to add more columnar trees including narrow conifers.