Don Kinzler, Published January 17 2014
Growing Together: Evergreens 101 – How to tell a spruce from a pine
I want all of us to be comfortable with the identification of common evergreens that grow regionally. If you have only a passing interest, this information might still be key someday. Imagine your specimen front-yard 30-year-old evergreen begins displaying rusty brown needles. You contact the nearest university’s horticulture department to determine how to save the featured tree. The first step in diagnosis will be the question “Well, what kind of evergreen is it?”
“Evergreen” is a broad term referring to plants, trees and shrubs that keep their green foliage year-round. In northern regions we usually think of evergreens having needles, but in milder climates leafy shrubs like rhododendrons retain their foliage all year and are called broadleaf evergreens. “Conifer” is a term for trees and shrubs that bear their seeds inside cones. Most conifers are evergreen and usually have needle-like or scale-like foliage.
Let’s learn the kinds of evergreens most common in our hardiness zone, starting with tree forms. Our goal is to identify the broad categories so we can call a spruce a spruce. In-depth study of individual named cultivars (cultivated varieties) will wait for another day.
Spruce is our most common evergreen tree. They are pyramidal in shape and can grow 40 feet tall with a base diameter of 15 to 18 feet. Two kinds are commonly found in our area. Colorado spruce and its blue cultivars have very sharp needles that are about one inch long.
Black Hills spruce is darker green with softer, shorter needles half an inch in length. Healthy spruce trees maintain branches all the way to the ground. It’s a matter of personal preference whether lower branches should be pruned and the trunk “elevated.” Personally, I prefer the natural look of branches sweeping at ground level.
Pines have longer needles than spruce. Their shape is pyramidal when young, but often becomes more informally rounded with age. Ponderosa pine can become 50 to 60 feet tall with a diameter of 25 to 30 feet. It is identified by long, waxy needles 4 to 6 inches long.
Scotch pine is also adapted to our climate and has needles 2 to 3 inches long. Height reaches 30 to 40 feet and bark becomes striking copper orange. White pine is occasionally seen but is better suited to the forested regions and soil types east of North Dakota’s Red River Valley. Needles are blue-green, soft and 5 inches long.
Larch. This species is interesting because it looks exactly like a needle-bearing evergreen tree during summer. But its needles turn golden yellow in autumn and drop, which removes it from the evergreen category, since branches are bare during winter. It is a deciduous (leaf-dropping) conifer.
Evergreens with shrub forms can be either tall or low-growing:
Junipers are a large group with foliage that looks more like prickles than needles. Pyramidal shapes grow 15 to 20 feet high such as Medora juniper. Juniper cultivars like blue chip become ground-covers growing to only 6 inches high, but spreading outward 6 to 8 feet. Other types grow from 1 to 5 feet high and spread outward. Junipers are sometimes called red cedar.
Arborvitaes are unique with flat, soft foliage instead of needles. Pyramidal or columnar cultivars can reach 25 feet tall with a narrow diameter of 3 feet. Globe arborvitae forms a perfect round basketball 5 feet high and wide. Lower growing versions of both globes and pyramidals are found in the nursery trade. Arborvitaes are sometimes called white cedar.
Yews are one of the most shade-tolerant evergreens for our area. Upright types grown in other regions generally lack hardiness, but there are several well-adapted spreading kinds that grow 2 or 3 feet high and spread outward. Needle length is about 1 inch and texture is soft.
Mugo pine is a shrubby pine with needles 3 inches long. The taller version can become 10 feet and sprawling. Dwarf Mugo pine maintains a neat mound 3 to 5 feet high.
Dwarf blue spruce becomes mound-shaped 3 to 5 feet high and 5 feet wide. Needle length and hue look much like the tree form Colorado Blue Spruce.
Now comes the quiz. As you drive around town, observe evergreens, their shape and characteristics. Try identifying them in a drive-by practice test. But have a designated driver. When I practice my identifying skills en-route, my wife Mary frequently reminds me that behind the wheel is neither the time nor the place.
Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler’s Greenhouse in Fargo. Readers can reach him at firstname.lastname@example.org.