A Prairie Garden Journal    by Dick Meyer

June is Tree Care Month

If it’s June (and it is), it’s time to think tree care.  April is the month of Arbor Day and tree planting, but for Wyobraskans, June is the most important month for tree care.  The main reason that June is the most important month for tree care in Wyobraska is that June is the best month for fertilizing trees—and fertilizing trees is just as important as fertilizing your lawn.  Wyobraskans all know what happens when they don’t fertilize their lawn for a couple of years—it loses its bright green color and barely grows.  The same thing happens to most trees growing in Wyobraska landscapes if they aren’t fertilized and properly cared for—they lose their dark green summer leaf color, their rate of growth slows, and they are left vulnerable to weather, insect, and other stresses. 

June is the best time to fertilize trees in Wyobraska because that is when the trees are best able to use the fertilizer.   If fertilized in early spring, trees will use the nitrogen to grow more and bigger leaves—not necessarily greener and healthier leaves.   For a tree, early spring fertilization is a lot like eating candy before dinner.  Likewise, fertilizing a tree in late summer in Wyobraska can cause the tree to continue to grow late into the fall—and put it at risk of serious injury from a hard early freeze—not an unusual thing in Wyobraska.  So June is the best month for fertilizing trees in Wyobraska—and July is also good, but why wait.

Most of the other tree care practices described in this column can actually be done at any time from March through November, but if you haven’t done them for your trees in recent years, June is a good month to catch up since you’re already out there fertilizing your trees—and that way your trees will be able to use the summer growing season to actually grow and to improve its health and vigor.

Previous Articles

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It's Finally Spring -  March 13

Spring Garden Calendar-March 20

No Garden Left Behind-March 27

Planting Trees for a Cooler Earth in a Warmer WyoBraska-April 3

Viburnums - Shrubs for Wyobraska Springs-April 10

Want A Water Conserving Lawn? You might already have one-
April 17

Creating Long Term
Tree-lationships April 24

Bigger, Bolder, Brighter,
Better—and Back In The Landscape May 01 & 08

Hardy Shrub Roses
May 15

Another Look at Native Plants
May 22

No Child Left Inside
May 29

J

2007 Articles

2006 Articles

Fertilizing trees with a major element fertilizer.

Major element fertilizers are the standard “tree and shrub” fertilizers.  They mostly contain nitrogen, phosphorus, and potassium—the three elements that plants need in fairly large quantities.  A good rule of thumb is to fertilize all of the area under the branches of a tree plus another 5 feet or so.  Use the following table to determine how much major element fertilizer to apply to each tree.  

Measure the tree diameter at 12" above ground or use height of evergreen tree.
Size of mulch circle in which to apply fertilizer.
Amount of fertilizer to use per tree or circle

The easiest way to apply the fertilizer is to spread it like you do a lawn fertilizer, using either a drop spreader or a “whirly-bird” fertilizer spreader.   If you have a nice, large circle of mulch around your tree (8’ diameter circle or larger) you may elect to simply spread about 2/3 of the amount of fertilizer suggested above within that mulch area, and water it in thoroughly.

Mulch.  Most landscape trees are planted in lawns, and trees and turfgrass are just not very compatible neighbors.  Grass growing right up to the trunk of a tree, particularly a newly planted or young tree, significantly slows the rate of growth of the tree.  That’s assuming that the tree isn’t fatally injured by the lawn mower or string trimmer.  Every tree needs a mulch boost at least every other year.  Mulch increases the rate of growth of young trees both by protecting the tree from the growth-slowing effects of lawn mower and string trimmer injuries and by improving the availability to the tree’s root system of needed soil elements, at least within the soil located immediately under the mulch.   A six foot diameter circle provides an adequate mulch area.  An eight foot diameter circle is even better.  A three to four inch deep layer of mulch is ideal.

Compost.  Over the course of one to three years, mulch also turns into compost for your tree.  To get the immediate compost effect, try adding a one inch layer of compost  under the mulch.  Mix the compost into the top one or two inches of soil with a hoe or shovel, then apply the mulch. 

Sulfur.  Sulfur changes the chemistry of the soil so that the roots of a tree can more easily pull elements like iron, zinc, and manganese out of the soil.  Sulfur is inexpensive, and easy to apply.  Sulfur needs to be in contact with the soil in order to do its work, so it needs to be place under the mulch.  If your tree is already mulched, rake the mulch aside.  Use three pounds of sulfur for a six foot diameter mulch circle, 5 pounds of sulfur for an 8 foot mulch circle.  Spread the sulfur fairly uniformly over the entire area, then work it into the top 2-3 inches of soil with a shovel or hoe.  (A sulfur and compost boost is a good combination.)  Reapply the mulch after you are done mixing the sulfur into the soil.  Don’t do this every year—once every five to seven years is all that is required. 

Minor Element   Minor element deficiencies are the primary cause of the summertime yellowing of leaves.  That yellowing is a sign of a serious minor element deficiency which is also leaving your tree vulnerable to insect and microorganism (bacteria & fungi) predation.  Spring is a good time to apply minor element fertilizer so that the tree has the opportunity to take up the elements prior to the coming growing season, but if you didn’t do it this spring, June is a good time to catch up.  Different minor element fertilizers have different application procedures.  Follow the directions for the product you select.