Dr. Leonard Perry, University of Vermont
In 2012 I began a trial site for a National Ornamental Grass trials, with 17 sites nationwide all testing several plants each of 17 switchgrass (Panicum) cultivars and 5 little bluestem (Schizachyrium). The photo is of the differences of the latter in pots, prior to planting out (left to right Minn Blue A, Prairie Blues, The Blues, Blaze, and Carousel). Here is the overview and update.
Due to the small size of many plugs, per our usual trial procedures here they were potted shortly after receipt into Jumbo square pots, ProMix medium with Osmocote 16-11-11 incorporated at 3.6oz. per cu.ft. (6lb. per cu.yd). Weak or poorly-rooted plugs were first planted into 4-inch squares, then when sufficiently rooted shifted into the Jumbo pots. Plants were grown in a nursery area throughout the summer, with planting delayed until early September due to an unusually dry and hot summer for this climate. Due to trial beds being unable to be watered often or easily, plants would have suffered or died if planted this past summer, plus all plants were not sufficiently and equally rooted until then.
The trial site is a full sun, rocky loam of low fertility (formerly a fallow grass field). At planting, 2 cups of local compost and slow-release 5-3-4 (one tbsp) were mixed with backfill soil. Plants were watered in, with little subsequent watering needed due to rain. No additional compost or fertilizer applications are planned for this coming season.
Soil and air temperatures are being recorded continually on hour intervals. With little snow cover during some quite cold periods this winter, this winter should be an excellent test winter for hardiness (with some replacements expected). Although the site is listed in USDA 4b, this is the first winter over the past decade it has not reached -20F air (missing by one degree on one day, 3 degrees off on another), making this a zone 5 winter. Yet one week later the air temperature peaked at 54F, a 73 degree range from the coldest point days earlier. Due to lack of snow cover during some of the colder periods, bare soil temperatures reached 23F for several days– the coldest in the 20+ years I have been recording such. However, with only 2 inches of snow (as was on the grass trial bed, usually), soil temperatures only dropped to 27-29F, but remained there for up to 3-day periods, again the coldest such soil temperatures I’ve recorded in the past 10 or so years.