CSU RESEARCH: 2021-22 Cool Season Trials Top Picks for Off-Season Color

By James E. Klett, professor and extension horticulturist, and Sheila Prentice, graduate teaching assistant, Colorado State University

This was the fourteenth year that Colorado State University (CSU) has conducted Cool Season Trials at the Annual Flower Trial Garden. The overall goal of this project is to determine which varieties of cool season plants are best suited for marketing and growing in the Rocky Mountain Region. Initial data was recorded in October 2021 and taken monthly, unless under heavy snow cover, until end of April 2022. Irrigation was monitored throughout the trial period and additional water was added when temperatures were above 40°F. Snow cover and rain amounts were recorded throughout this period.

The winter and early spring 2022 had some different weather periods. There were lengthy periods of snow cover in January and February 2022. April was extremely dry, having with very little or almost no rain, with extremely high winds. Also, on the evening of April 12, the low temperature dropped to 16°F after several very warm days in early April reaching 80°F.

Representatives from the CSU Annual Trial Committee met on April 27, 2022 to evaluate 57 different varieties of Cool Season plants. Unlike last year, there were no geese problems because almost all of the kale and cabbage varieties did not survive the cold temperatures encountered.

The committee recommended five superior varieties from the 2021-22 Cool Season Trials. For more information, visit www.flowertrials.colostate.edu and click on Cool Season tab.

Viola cornuta Penny™ Violet Tiger Face from Syngenta Flowers

The rich velvety purple flowers had a bright yellow center, making a nice contrast. Cute whiskers made the flower even more attractive. Uniformity of this variety was striking. One evaluator described the plants looking like “little soldiers” in a perfect row. Winter survival was perfect—no losses or dieback.

Viola x wittrockiana Delta™ Premium Violet and White from Syngenta Flowers

Flowers on this variety were extremely large and the dark purple color combined with white provided a very crisp pattern. Plants had good vigor and excellent uniformity. Flowers had a great flower power, facing upward and almost obscured the vegetation.

The following varieties of Freefall series from Syngenta did extremely well in our Cool Season Trials due to their vigorous spreading. Plants looked good in the ground but could work well trailing over the side of containers.

Viola x wittrockiana Freefall™ Golden Yellow from Syngenta Flowers

Flowers were a golden yellow which showed very well against darker green foliage. Winter hardiness was excellent. The golden flowers on this variety would brighten any landscape on a cloudy, dull-weather day.

Viola x wittrockiana Freefall™ Mariana from Syngenta Flowers

This variety was noted for its strong vigor and classic blue and white pattern. Flowering was prolific and it had an excellent mounding growth habit and good uniformity. One evaluator descried the flower color as, it “speaks spring.” It definitely had a welcome color after a long winter.

Viola x wittrockiana Freefall™ Sundown from Syngenta Flowers Flowers had good depth of color with a nice contrast between dark violet and yellow. Winter hardiness was excellent without any losses or dieback. The whiskers on the flowers were an added bonus on the abundant flowers. The plants and flowers had a nice size and were very uniform.