When you hear the word “evergreen,” you probably think of a Christmas tree or that beautiful pine tree out back that Johnny brought home from school when he was in the third grade.
In botany, the definition of evergreen is “a plant that has leaves in all four seasons or is always green.” Evergreens include groups of plants like conifers, live oaks, holly, rhododendrons and an ancient group of gymnosperms such as cycads, which are common in southern locations. Rainforests, most of which are in frost-free parts of the world, are almost all evergreen. These plants grow new leaves to replace older leaves damaged by weather, insect and disease.
So, in short, a plant like the Christmas Poinsettia is an evergreen (a shrub or hedge) in Florida, but a tender annual or houseplant in the Midwest. The holly we see on Christmas cards and in fresh arrangements during the holiday season is an evergreen in the South but is not winter hardy here. There are a few select varieties of holly that will grow in our temperature zone 5. The holly or winterberry we have at the Bickelhaupt Arboretum is Ilex. It sports prolific bright red berries and beautiful fall leaves, which are deciduous; therefore, it is not an evergreen. Rhododendrons and some azaleas hold their leaves all winter making them broadleaf evergreens, dropping leaves only when the winter temperature falls below zero.
Pines are evergreens but so are fir, spruce, arborvitae, cedar and hemlock. To be more specific, these trees and shrubs are in a class called conifers. Conifer is a compound Latin word of conus an ferre meaning “the one that bears cones.” The definition from the Merriam-Webster dictionary reads, “a bush or tree that produces cones and usually has leaves that are green all year long.” Conifer leaves are mostly needle leaves like pine and fir or scale-type leaves in the case of arborvitae and juniper.
The cones are the hard structures that produce and protect the seed. Most cones take two years to develop mature seeds. The first year green cones remain tight or closed. The second year as the scales dry and turn brown they open up and the seeds are dispersed. The cones develop the first year and they drop the second year.
We call all cones, pine cones when actually spruce trees produce spruce cones, fir trees produce fir cones, cedar trees produce cedar cones and so forth. I am sure we will still call all cones, pine cones unless it comes up in a trivia contest… you might just have the winning answer if you answer arborvitae cone.
In nature, animals and birds help to disperse the seeds. When I was very young, I tried to germinate conifer seeds without much luck. I could not “Google” information back in the 1960s, so I did the next best thing and asked my dad if he had any ideas on how to get a better germination. I was surprised at his response. He told the story of an old German nurseryman who would feed pine seeds to his ducks and then spread their manure on a seed bed and cover it with soil and a layer of leaves. Tiny seedlings would appear the next spring. I just took his word for it and decided to germinate easier types of trees!
Most evergreens or conifers can be trimmed lightly for fresh greens to decorate for the holidays. Keeping the greens cool and out of the sun will keep them fresh and fragrant for several weeks.
Margo Hansen is a horticulturalist and director of programs at Bickelhaupt Arboretum. She is the host of the “Great Green Garden Show” on KROS Radio.