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Tales from a Plant Addict

Fun (& a few serious) facts, tips and tricks for every gardener, new and old.

Planting Trees

Last week's column discussed choosing trees suited for particular parts of your landscape. In Extension, we like to say "Choose the right plant for the right place". Once you've chosen the right site and the right kind of tree for that site, now just buy one and plant it, right? Not quite.

When looking at trees for sale, buy the best quality you can. This may mean buying a smaller tree, but in the long run will save you a lot of work and may even save you from replacing the tree in a few years. If a tree looks distressed, diseased, or weak, your best choice is another tree.

Trees that wobble in their pot or burlap probably don't have good root systems. Container-grown trees that have a mass of circling roots in the pot are the other extreme. These roots will continue to grow in circles unless they are removed, and even then it can take longer than usual for a tree like this to establish itself in the landscape.

When ready to plant, think about digging a planting bowl rather than a planting hole. Generally speaking, most of a tree's roots are in the top 12 to 18 inches of soil. Digging a deep hole does nothing to help the roots grow out into the soil. A nice wide hole creates a soil environment that new roots can penetrate easily and allow the tree to establish and anchor itself in the landscape.

The U of I does not recommend amending the soil in the planting hole. The thinking behind this is that amendments in the planting hole creates a region of slightly better soil that the roots are happy to stay in rather than branching out into the surrounding soil. If the roots don't extend out into the surrounding soil then anchoring and establishment of the tree is slowed.

Although I understand this reasoning, I have personally encountered soils that are nearly impossible to plant in as is. I have talked to people that had to use a pickax to make their planting hole because the soil was extremely heavy clay. Instead of a pile of soil next to the planting site, it was hard clay chunks. In those cases I would consider a 50/50 mix of topsoil or compost along with the native soil so that there is good soil contact around the new planting instead of a loose pile of clay chunks.

You might remember being taught that trees shouldn't be planted deeper than they were in the pot or the burlap. This is still true, but more often than not they are actually too deep in the pot or burlap to start with. Don't be afraid to remove some of the soil near the base of the tree to look for the trunk flare, the area that gets a little wider where the first roots extend outward. Think of how a child typically draws a tree with the little slope at the base. This really exists. Look for it.

This is the depth at which the tree should be planted, or even a little above to allow for settling. Also remove as much of the burlap, rope, or wire as you can. Some people argue that these materials will rot away underground. I have witnessed with my own eyes trees planted over ten years ago that either had problems or had died that upon inspection revealed intact burlap, rope and wire around what had been the trunk and/or root ball. None of these materials magically go away in a short time—and they impede the tree's growth, shortening its life. Furthermore, trees planted deeper than the trunk flare will likely develop problems with the roots in future years, which will also shorten its life.

After planting, your job is still not done. Adding a layer of mulch around a newly planted tree will help conserve moisture and suppress competing weeds. Mulch should not touch the trunk, but should be arranged to create a dish or bowl shape about two to four inches deep with the tree in the center. This helps direct water towards the tree.

Research shows that trees establish themselves more quickly in the landscape if they are not staked. Being rocked by the wind actually stimulates roots to grow and anchor the tree. I know this to be physiologically true, but practically speaking if your tree is uprooted by the wind, that doesn't do much for root growth! If you live in a very windy area, it may be a good choice to stake your tree. There are lots of systems out there, but whatever you choose make sure that it does not injure the bark of the tree. Bark injury can result in disease or even limb or total tree death. Remember to remove the staking after about a year of growth.

Keep the soil moist but not soggy around your tree after planting. If the soil under the mulch is dry, it's time to water. A retired local municipal forester shared his rule of thumb for watering trees with me recently. He recommended watering trees for one year for every inch of trunk diameter plus one year. So a tree with a trunk diameter of three inches should get supplemental water for four years. He told me that every single time he tried to shorten the supplemental watering time for a tree, the tree ultimately died. Keep in mind also that in extreme drought conditions, even established trees need water!

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