Fig. 1. Visual estimates of percentage ground cover during plot establishment; plots were seeded on 24 September 2002 (day of year 267). Species/cultivars include tall fescue (TF), Kentucky bluegrass (KBG), and two hybrid bluegrasses (HBG1 and HBG2). Symbols plus (+) below the data indicate significant differences (P < 0.05) between one and the other three species/cultivars, diamond-plus (diamond +) indicate significant differences among all species/cultivars except two, and the letter (x) indicates significant differences among all species/cultivars on a given day.

Image from Applied Turfgrass Science article:
Performance in the Transition Zone of Two Hybrid Bluegrasses Compared with Kentucky Bluegrass and Tall Fescue