Spring is only the second best time to feed trees
CARTHAGE, Mo. – The best time to fertilize trees is in the fall, but if you missed that opportunity, the second-best opportunity is in March and April.
“Trees seldom need fertilizer, especially if they are in a fertilized lawn area where the fertility level is maintained. However, some trees are grown in soil lacking fertility,” says Robert Balek, horticulture specialist with University of Missouri Extension Service.
However, raking and removing leaves routinely from under trees removes nutrients from the root zone and depletes the soils fertility around the tree.
A soil test from the nearest MU Extension Center will help accurately determine the level of fertility in the soil around trees.
“But you can also determine a tree’s fertilizer needs by measuring the amount of growth it puts on each season,” says Balek.
To determine the growth rate of a tree, Balek suggests measuring from the tip of a branch, (terminal bud) down to the growth collar. This distance shows how much growth occurred last season. Then from that growth collar down to the next gives the previous year’s growth.
“Younger trees should have 6-12 inches of new growth. Mature trees should have around four to six inches,” says Balek. “If the seasonal growth looks diminished, it may be due to a lack of fertilizer.”
Other factors that can cause diminished growth include careless planting, improper watering, poor location, and unsuitable climate conditions. Fertilizer cannot help these situations. Small leaves, yellowing, and lack of vigor may also be signs of low fertility.
If the tree needs fertilizer, the recommendation is a 2-1-1 or a 3-1-1 ratio (nitrogen-phosphorus-potassium). Fertilizer is applied under the tree branches and an additional four to six feet out.
“Calculate the area of this space and broadcast about two pounds of Nitrogen per 1000 square feet for spring applications,” advises Balek. “An alternative to broadcast is to drill holes 6 inches deep in a scattered pattern and add fertilizer, then cover with compost or sand.”
Most lawn fertilizers available in spring are suitable for fertilizing trees. An exception is fertilizers containing broadleaf herbicides such as 2,4-D or dicamba because these herbicides can damage trees.
Fall fertilizer application rates will differ. See MU Extension publication “G6865, Fertilizing Shade Trees” at http://extension.missouri.edu/p/G6865 for details.
For more information, contact one of MU Extension’s horticulture specialists or educators in southwest Missouri: In Greene County, Patrick Byers or Kelly McGowan at (417) 881-8909 or in Jasper County, Robert Balek at (417) 358-2158.