Dynamic Duo can be applied any time of year within the growing season with no risk of burn and used as directed. Multi-use, safe and effective all summer long – for flowers, shrubs and trees, top dressing. For cool season grasses: Kentucky bluegrass, Turf-type Tall Fescue,Fine Fescue, Bentgrass and Perennial Ryegrass. For warm season grasses: Common Bermuda, Hybrid Bermuda, St. Augustine, Centipede and Bahia.