Elms should be fertilized once or twice a year.  However, not just any fertilizer will do and using the wrong type of fertilizer can actually increase the chances that your tree will contract Dutch elm disease.  Avoid standard "one-size-fits-all" lawn and turf fertilizer.  In particular, fertilizers that release large amounts of Nitrogen quickly into the soil can encourage structurally weak growth that could attract the elm bark beetles carrying the Dutch elm disease fungus.  Aside from the formulation, the method of fertilization differs from that of your grass.  In order to give your trees the most benefit, the fertilizer must be placed below the grass roots.

To find out how to obtain fertilizer specially selected for use on elm trees, click here.