HORTSERVICESFertilization and Pre-emergent weed control - Fertilization is done on a modest scale and is accomplished in the fall for most trees and shrubs. Perennials and annuals are generally done in the spring when growth first begins. Slow-release granular materials are used in both instances. Pre-emergent weed controls are generally applied twice per year, usually in Feb/March and again in Aug/Sept. This type of weed control for ornamental beds is either applied as an over-the-top granular material or is sprayed on the beds.