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Using Organic Mulches

Apply an organic mulch on most established ornamental plants in mid-spring when the soil has warmed sufficiently for active root growth.

Contributors: Michigan State University

  Using Organic Mulches                  

By Michigan State University - Extension

When to Apply Mulch                                         


Apply an organic mulch on most established ornamental       

plants in mid-spring when the soil has warmed sufficiently  

for active root growth.  If applied before this time, the   

mulch will keep the ground cool and root growth may be retarded. 

Apply an organic mulch  around newly set ornamental plants after they

are put into place and thoroughly watered.                               


How Deep to Apply Organic Mulches                           


For best results, apply mulch at least 2 to 4 inches deep   

over the whole area anytime during spring, summer or early fall    

but avoid covering the crowns of very low-growing           

ornamental plants.  Tender ornamentals that need winter     

protection may require an additional 1 to 2 inches of       

mulch around the crowns or bases of the plants during the   

winter.  In the spring, this added mulch should be fanned   

out or away from the stems or crowns of the plants before   

more material is added for a summer mulch.                  


Fertilizing Organically Mulched Plant Material              


As indicated previously, mulching with many organic         

materials--including wood chips, sawdust, straw or          

shredded bark--means you must apply extra fertilizer        

around the plants to reduce the chance of nitrogen          

deficiency or starvation.  Apply 1/4 pound of ammonium      

nitrate or ammonium sulfate for each bushel of mulch        

material used on the  bed, or 2 pounds per 100 square feet  

of a complete fertilizer such as 5-10-5, 12-12-12 or        

similar analysis.  This fertilizer should be applied        

before the mulch is placed on the soil, or in early spring  

before more material is added to plants already mulched.    

If the lower foliage yellows and the plants lack vigor      

during early summer, apply additional fertilizer.           


Do Not Over mulch                                            


The roots of plants need a constant supply of oxygen  at    

all times.  Over mulching kills the roots of shallow-rooted  

plants by suffocation.                                      


Symptoms of too much mulch include chlorotic foliage        

(symptoms often resemble iron deficiency), abnormally       

small leaves, poor growth and dieback of older branches.  


Disease organisms that are active under conditions of low

oxygen and excessive moisture can become active and

attack  the roots.  Sometimes the old root system will be

rotted  as the plant tries to send out new roots into the mulch layer. 

Excessive amounts of mulch applied around tree trunks can lead to

cankers on susceptible species.       

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