Unlike turf fertilization, which is done from the surface of the lawn, providing an effective feed for trees and shrubs should be done at the root-zone level using a method called Deep Root Feeding. Liquid fertilizers are injected directly into the root-zone where they can be easily and directly accessed by the roots. The nutrients provided by the deep root feed allow the development of enhanced growth and vigor above ground as well as root development below. Plants will become healthier overall and more resistant to disease and insect infestation.
So which trees and shrubs benefit from deep root feeding? While established shade trees do not necessarily require additional fertilization, ornamental trees and shrubs and especially those that are newly-planted or located in nutrient-deficient soil will benefit greatly. Trees and shrubs that are recovering from pests or disease also recover more quickly when provided with additional nutrients. Deep root feeds can ideally be done in either spring or fall when cooler nighttime temperatures allow for more efficient uptake of the feed.