Many Landscape Grasses Survive Long-term Hardiness Trials in United States Department of Agriculture Plant Hardiness Zone 4b

Abstract

A long-term, landscape grass hardiness study was initiated in Summer 1987 at the University of Minnesota Landscape Arboretum in Chanhassen, MN, USA [United States Department of Agriculture Plant Hardiness Zone (USDA PHZ) 4b, –20 to –25 °F]. This location averages a 158-day growing season (frost free), summer temperatures of 79.9 °F, and winter temperatures of 10.4 °F. Over 35 years, 392 different kinds of plants from the grass (Poaceae) and sedge (Cyperaceae) families were planted to evaluate winter survival, landscape value, flowering, and pest resistance. Most plants (n = 271, 69%) survived at least 4 years, 186 (47%) survived 10 years, 81 (21%) survived 20 years, and 29 (7%) survived 35 years. Sixty-eight plants (17%) were deemed not winter hardy in this location (USDA PHZ 4b), and 53 are listed with insufficient data for a hardiness rating. Changes in maintenance as well as challenges encountered with long-term trials of herbaceous plants are discussed.

Keywords

• miscanthus
• ornamental grasses
• pennisetum
• winter hardiness