CSU Research

Use these columnar trees and shrubs in small spaces

Colorado State University researchers continue to evaluate over 1,300 taxa of woody plants for adaptability, ornamental flowers, fruit, fall color and pest problems. Of recent interest, are woody plants with a columnar growth habit that can be planted in residential areas with limited space between homes. Eight such plants presented here are proven adaptable to

Colorado conditions. | CG

Carpinus betulus ‘Frans Fontaine’ (Frans Fontaine Hornbeam)

The narrow, columnar shape of this tree is maintained to maturity. It grows to about 20 to 30 feet in height with a width of 10 to 15 feet. Its dark green leaves turn yellow in the fall. Tips & Tricks: The current season’s growth curves inward toward the central leaders.

Celtis occidentalis ‘JFSKSU1’ – Prairie Sentinel ® Common Hackberry

This clone was discovered in rugged high plains of western Kansas. It has a tightly fastigiate columnar growth habit, maturing to about 45 feet in height and 12 feet in width. Medium green leaves turn yellow in the fall. It adapts very well to prairie heat, drought and cold. Tips & Tricks: Use this tree for narrow city streets in the toughest conditions.

Juniperus scopulorum ‘Woodward’ – Woodward Rocky Mountain Juniper

This juniper was organically found in western Oklahoma and has a narrow/columnar growth habit with blue/green needles. A Plant Select® recommendation, the plant is well adapted to Colorado conditions. It appears to be a male since no fruit has been observed. Tips & Tricks: It is a good tall screening juniper and appears less prone to snow damage but could be in limited supply.

Malus ‘Adirondack’ – Adirondack Crabapple

This clone is a United States National Arboretum introduction with excellent disease resistance. It has an unusual narrow vase shape/habit to about 18 feet tall and 10 feet wide. The red flower buds open to white single flowers, and its dark green leaves

turn some yellow in the fall. Tips & Tricks: The tree bears some light red to orange fruits about 3/8 inch, which don’t last long.

LEGEND

Full sun

Adapts to part shade

Prefers shadier conditions Useful for containers

Xeric

Requires moisture

Requires more moisture

Contributed by James E. Klett, Ph.D. Colorado State University, Department of Horticulture and Landscape Architecture

Ostrya virginiana – American Hophornbeam

This graceful small tree with drooping branches matures to a more rounded habit. The gray/brown bark grows in long, narrow strips, and the tree’s dark green leaves turn yellow in fall. It has male catkin fl owers in spring and fruit that resembles hops in late summer into fall. Though it is an understory tree, it can tolerate full sun. Tips & Tricks: The tree can be a little slow to re-establish after transplanting.

Quercus robur x alba ‘Crimschmidt’ – Crimson Spire ™ Oak

Crimson Spire is a hybrid of white oak and columnar English Oak that is resistant to powdery mildew. It has a columnar/fastigiate growth habit with blue green foliage that turns rusty red in fall. It is adapted to more alkaline soil and matures to a height of about 45 feet tall and 15 feet wide. Tips & Tricks: It is a great choice where a tall narrow tree is needed, and holds brown leaves though winter.

Quercus robur x bicolor ‘Long’ – Regal Prince® Oak

A hybrid between columnar English Oak and swamp white oak, this tree has glossy dark green leaves that turn yellow in the fall. It has an upright, broadly columnar growth habit that grows to about 40 feet tall and 20 feet tall. Tips & Tricks: It is tolerant of clay soils but may not thrive if soil is too alkaline. It is resistant to powdery mildew but could have some aphid problems and sooty mold problems.

Hibiscus syriacus ‘Gandini Santiago’ Purple Pillar ™ Rose of Sharon

This clone has a columnar growth habit that grows 10 to 15 feet tall and 2-3 feet wide. The fl owers— short-lived, sterile and semidouble—are pink with a purple eye and bloom from July to September. Once established, the plant can tolerate heat and

dry soils. Tips & Tricks: It is a good vertical accent shrub which can be used as a tall screen.