In the Garden | Going native with evergreens

Chicago
By Chicago 6 Min Read

The East Central Illinois Master Naturalists are hosting their Annual Native Tree and Shrub Sale with ordering available now until Oct. 13. More info is at go.illinois.edu/Natives.

I am often asked for tree-planting recommendations, with many potential planters seeking the perfect evergreen species to plant in East Central Illinois.

While my first thoughts typically go to the area’s only native conifer, eastern red cedar (Juniperus virginiana), some folks are less than thrilled with its sometimes-unsymmetrical growth habit. I think that is a plus, adding to the visual interest of the plant, but it doesn’t always create the perfectly pyramidal effect that many desire.

My next recommendation, for those leaning more toward a pyramidal or conical-shaped plant, is usually white pine (Pinus strobus). It is a fast-growing and majestic tree that is native to Illinois, although its home range lies far north of our area. White pine can grow to 100 feet or more on good sites and is known across eastern forests for its straight, tall trunks, often noted as a New England favorite for sailing masts in years past. It is a versatile and adaptive tree with home range that extends across much of the eastern U.S.

However, white pine is notorious for suffering from environmental stress, which often becomes most apparent this time of year as drought pressure builds. Much of this stress is related to site conditions, as white pine is intolerant of soil compaction, high clay content and overly alkaline soil, all of which are typical in urban soils. While the plants may grow rapidly in youth, as they mature, this stress starts to become apparent and slowly builds to more drastic symptoms or dieback.

While I still do recommend white pine as a great option for someone in search of an Illinois-native evergreen, assessment of site conditions needs to be done prior to planting in urban areas. A simple soil test can identify high soil pH (alkalinity), which can be addressed with surface-applied granular products that slowly shift pH to more acidic conditions.

However, assessing soil compaction and past soil disturbance can be tricky. I know I often think of soil compaction as a condition created by heavy equipment or extensive traffic in one area, but some of our basic lawn care activities, such as mowing, can contribute greatly over the years. So it’s a safe bet that some level of compaction has occurred in areas of turfgrass with a history of mowing and lawn care. If you combine additional traffic on the soil surface, even for a one-time event like heavy foot traffic during re-roofing or equipment access for home foundation work or additions, soil compaction can become extreme, which is very slow to naturally correct, or may simply not be repairable.

While we can pretty easily create favorable conditions in the planting hole or immediately around the tree at planting time, consider the mature root zone of the plant. Research has identified the common root spread of a mature tree to be up to three times the branch spread, which can occupy a huge space.

As trees mature, the spread of their root system needs to keep pace with the amount of branches, limbs and leaves that need moisture and nutrients from the soil to stay healthy. Soil compaction can limit the rate of root spread, slowing the development of a sustaining root system.

If you add in a driveway, sidewalk, street or other impervious surface, the inaccessible areas created by hard surfaces can drastically limit the trees ability to expand its root system over time. The result of these stresses may not be apparent until the tree reaches a large size, needing a large root zone that it cannot support.

At planting time, I think it certainly pays to think about the mature root zone of tree, but few planting locations in the home landscape can offer ideal conditions. So don’t drive yourself crazy trying to figure out where a white pine may fit in your space. If you are considering planting a native evergreen and have concerns about site conditions, I often recommend eastern red cedar, which is a really tough tree that can handle a wide range of soil conditions.

I find that most evergreens are sensitive to our soil conditions since most are not native to East Central Illinois. Although that evergreen foliage is desirable, a native deciduous tree is often a better choice.

Fall is a great time to plant trees, but it always pays to do some homework ahead of time prior to adding one of these long-lived perennials to your landscape. For more information on tree planting possibilities check Illinois Extension’s tree selecting website at go.

illinois.edu/treeselector.

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