National Arbor Day, a day for celebrating the contributions of trees, is next Friday, April 28th. The first Arbor Day took place on April 10, 1872 in Nebraska. J. Sterling Morton, who was the secretary of the Nebraska Territory at the time, first proposed a holiday for the planting of trees as a member of Nebraska’s State Board of Agriculture. The first Arbor Day included prizes for the people and communities that planted the most trees. It was a huge success with over one million trees planted. Soon after, Kansas, Tennessee, Minnesota, and Ohio all joined in with tree planting holidays of their own. National Arbor Day is now celebrated as the last Friday in April.
Tree Selection
Now that we are in the tree planting mood, let’s go over how to choose a good tree and then plant it properly. Starting off with a quality tree will be a good start to planting a tree that performs well in the landscape. Quality trees can establish quicker, be healthier, withstand storms, and live longer than lower quality trees.
You may want to buy the largest tree you can find. However, larger trees take much longer to establish and require much more irrigation than smaller trees. Smaller trees are better suited for poorly drained sites since their root-ball is shallower.
The root flare is the part of the tree where the roots “flare” off the trunk. In a nursery tree the root flare should be easy to spot. It is like the base of a wine glass where the stem of the glass meets the base. If the tree trunk emerges from the container like a fence post, then the tree is too deep in the container. Before planting, you will need to remove the potting media that is over the root flare.
Large extensive roots that circle around the inside edge of the container are considered defects. The circling roots should be cut. A tree with extensive large circling roots will be damaged too much by the procedure. Roots that are wrapping around the trunk are called girdling roots. These roots will eventually choke out the tree and will need to be cut out as well. Both circling roots, and girdling roots are defects that should be avoided.
Trees with poor trunk structure will require more over the life of the tree. Poor trunk structure is correlated with less wind tolerance as well. Purchasing a tree with good trunk structure will pay off as a safer tree in the long run. Poor quality trees branch off into two or more main trunks. It may look nice, but it is a defect with long-term consequences. Good quality trees have a single trunk and one dominant leader. Of course, trees that are typically multi trunked such as ligustrum and chaste tree are naturally found as multiple trunked trees and do not have to be corrected.
Tree Planting
When planting a tree, the planting hole is very important. The most common mistake is to dig it too deep. The old rule of thumb was that when planting a tree, place it so that the level of the soil in the pot was level with the natural soil surface. This method is no longer recommended. The hole should be dug a little bit shallower than the container, and as wide as you can possibly make it. A good practice is twice the diameter of the root ball. An easy way to remember not to dig the hole too deep is to use a saying a wise forester once told me; “Plant it high, and it won’t die”. When a tree is planted deeper than it should be, the root system is starved for oxygen, and the tree does not become established in the landscape. Also, with trees planted too deep, the trunks are covered with soil, promoting decay situations.
After removing the tree from the container, the rootball should be inspected for circling or girdling roots. Circling roots can be corrected by shaving or cutting off the outer edge of the root ball at planting. The tree should be set so the root flare is placed slightly above the natural soil level. No soil should be placed on top of the root ball when backfilling the hole. The soil removed when digging the hole is the best soil to put back in the hole when backfilling. No amendments like fertilizer or manure should be added to the hole.
The final step is to provide adequate water for your tree. The water provided by most sprinkler systems is not enough for establishing trees. Regular frequent irrigation after planting helps a tree to establish quicker. When watering, apply 2-3 gallons of water per inch of trunk diameter of the tree to the root ball. For instance, a two-inch diameter tree should receive between 4 and 6 gallons of water at each watering session. This should be done every day for a month, then every other day for two months. Large trees greater than 4 inches need additional irrigation. Mulching the area around the tree after planting provides a place for the new tree roots to grow without having to compete with turf roots. Mulch also adds organic material to the soil as it decomposes. A three-inch-deep layer of mulch placed in a 6-foot diameter circle around the tree, but no closer than 6 inches to the trunk of the tree, will help the tree establish quicker.
For more information on arbor day, selecting trees, or planting trees, go to: http://www.arborday.org ; https://hort.ifas.ufl.edu/woody/documents/ch_10_mw04.pdf; and https://hort.ifas.ufl.edu/woody/documents/EP314.pdf.
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