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Illinois Natural History Survey Circular 56 



When should you fertilize and with what? 



Free branch and trunk growth occurs primarily during May, 

 June, and July, but roots grow and a( tively absorb nutrients 

 throughout the year whenever the soil temperature is above 

 40° F. Scheduling of the time and rate of application will 

 depend on the types of fertilizers to be used. 



Time of application 



Nitrogen fertilizers should be applied annually. Little 

 available nitrogen remains in the soil from year to year, since 

 most of it is used by plants or carried away by water. Nitrogen 

 fertilizers are most efficiently utilized by trees when applied 

 in April or May; however, applications in October or 

 November will stimulate growth the following year. 



Phosphorus and potassium fertilizers are chemically bound 

 in the soil and become available slowly throughout several 

 growing seasons. They should be added to the soil every 3-5 

 years in spring or in fall, whichever is more convenient. 



Figure 4. Stakes have been placed at the four corners of the area to be fertilized. 

 They are far enough from the tree so that its entire branch spread is included. 



