By Mary H. Meyer, P. Bennett, B. Fair, J. E. Klett, K. Moore, H. B. Pemberton, L. Perry, J. Rozum, A. Shay, and M. D. Taylor
Table 1. Collaborators and trial location information for national grass trials, 2012-15. z 1 inch = 2.54 cm.
Switchgrass and little bluestem are native grasses found throughout most of the U.S. With this large native range, individual plants often exhibit considerable variation in height, foliage color and plant form. With many cultivars now available of these two grasses, we wanted to evaluate landscape performance of as many cultivars as possible of these species across the U.S.
Collaborators in eight states — Colorado, Minnesota, North Carolina, Ohio, Oregon, Pennsylvania, Texas, and Vermont (Table 1) — grew 17 switchgrass (Panicum virgatum) and five little bluestem (Schizachyrium scoparium) cultivars. Four additional locations in Florida (Fort Lauderdale, Fort Pierce, Quincy and Wimauma), Nebraska (Lincoln), and Texas (Lubbock and San Marcos) completed one or two years of the trials.
Plants were established in 2012 and data was collected during a three-year period from 2013-2015. Plugs from four growers — Kurt Bluemel Inc., (Baldwin, Md.); Emerald Coast Growers, (Pensacola, Fla.); Hoffman Nursery, (Rougemont, N.C.); and Walters Gardens, (Zeeland, Mich.) — were field planted with irrigation as needed the first year and minimal watering and management in the following three years. Most locations used organic mulch to control weeds.
Collaborators were asked to compile annual data on plant height; width; flowering time; fall color; pests; foliage color determined by Royal Horticultural Society’s color chart; plant form; flowering date; floral impact; self-seeding; winter injury; landscape impact; and mortality. Not all locations compiled all data, however height, width, survival, floral impact, landscape impact, and plant form were recorded at all of the eight locations that trialed plants for the full four years.
Three of the 17 switchgrass cultivars, ‘Cloud 9’, ‘Northwind’, and ‘Thundercloud’, had a rating of 4.0 or higher (on a 1-5 scale) when averaged over six or more locations for three critical traits: plant form, floral impact, and landscape impact (Table 3).
‘Shenandoah’ and ‘Warrior’ switchgrass had a rating of 4.0 or higher averaged over six or more locations for plant form and landscape impact, but not floral impact (Table 3). Only one of the five little bluestem cultivars, Blue Heaven, rated 4.0 or higher for plant form and landscape impact when averaged over six or more locations (Table 2).
ABOVE: From left. Little bluestem ‘Carousel’, ‘Jazz’ and Blue Heaven in Minnesota Landscape Arboretum grass trials, 2015. BELOW: Variation in switchgrass height and color in National Grass Trials. From left, ‘Hot Rod’, ‘Shenandoah’, ‘Heavy Metal’ and ‘Dewey Blue’. RIGHT: From left, ‘Carousel’, ‘Jazz’, Blue Heaven and ‘Prairie Blues’.
Texas A&M Agricultural Research and Extension Center, Overton; Florida (Fort Lauderdale, Fort Pierce, Quincy and Wimauma), and Vermont had the highest mortality rate. Southern Florida locations lost 50 percent of their plants by the end of 2014. Wide variation was reported for landscape impact, individual cultivar height and width from different regions of the United States.
z Flor = Floral impact: 0 = dead; 1 = no impact (no inflorescence present); 2 = 25% impact; 3 = 50% impact; 4 = 75% impact; 5 = 95% impact, very showy. y Form = Plant form or overall growth habit: included uniformity and lodging 0 = dead; 1 = 80% or more of the plant is prostrate; 2 = approximately 66% of the plant is prostrate, or is lodged or is in any way ‘non-uniform; 3 = 50% lodging or prostrate; 4 = 80% or more of the plant is upright, uniform, very little lodging; 5 = 95% or more of the plant is upright, uniform, attractive, very ornamental, no lodging; na = no data available. x Land = Landscape impact: 0 = dead; 1 = Very little or no ornamental value in the landscape. Growth weak with poor foliage color, high rate of lodging, little flowering (if flowers should be present) and/or high rate of disease or insect damage; 2 = Below average landscape appearance and value. Vigor poor with significant problems with plant habit and/or disease or insect damage; 3 = Average landscape appearance and value. Vigor good, but with some problems with plant habit, and/or disease or insect damage; 4 = Above average landscape appearance and value with only minor problems with plant growth habit and disease or insect damage; 5 = Outstanding landscape appearance and value. Good vigor, foliage color, and flowering (if flowers should be present), with little or no disease or insect damage. (adapted from Pemberton and Roberson, 2001); na = no data available.
Individual results by year are online at the National Grass Trials site grasstrials.com. This range of variability in landscape plant performance demonstrates the importance of local plant evaluations. Complete data can be found in the published final report below by Meyer et al., 2017 in HortTechnology.
References:
Meyer, M. H., P. Bennett, B. Fair, J. E. Klett, K. Moore, H. B. Pemberton, L. Perry, J. Rozum, A. Shay, and M. D. Taylor. 2017. Switchgrass and little bluestem cultivars show performance variation across eight states in National Grass Trials. HortTechnology 27:731-738. doi: 10.21273/HORTTECH03795-17.
Meyer, M.H. 2017. National grass trials. 14 July 2017. https://grasstrials.com.
Pemberton, B.H. and W. Roberson. 2001. The East Texas bedding plant pack and garden performance trials. HortTechnology 11:392-396.
