CSU perennial trials reveal top 5 performers in Rocky Mountain conditions

After three seasons growing in the challenging conditions of the Rocky Mountains, five perennial plants have been named “Top Performers” by researchers at Colorado State University.

Evaluating perennials in the Rocky Mountains

The purpose of the trial garden is to evaluate new perennial plant species and cul­tivars under the unique Rocky Mountain environmental conditions. Plants are evaluated for plant vigor, uniformity, floriferousness and tolerance to environmental and biot­ic stresses. The Perennial Trial program at Colorado State University is designed to test newer perennial cultivars that have been introduced in the past three years or less. Entries in this trial are grown for three summers and two winters before they are switched out for new entries.

About the Trial Garden

CSU’s Flower Trial Garden, which draws thousands of visitors each year, relies on student gardeners, volunteers and industry supporters and experts who help provide detailed analysis of plant performance. Colorado State Extension master gardeners play an essential role in planting and maintaining the garden. The outcome of this research is valuable to the industry and home gardeners alike. That’s because the Rocky Mountain region has unique growing conditions, characterized by high altitude, intense solar radiation, drying winds, severe hailstorms, large fluctuations between day and night temperatures and a season-long need for irrigation.

The Perennial Trial Garden receives no direct state or public funding. It is funded primarily by fees from plant-breeding companies that submit entries to the trials. The garden also receives donations from industry associations, foundations, nurseries, plant producers and other companies in the green industry.

Performance Evaluation

Photos and data on plants and flowers were collected biweekly from May to early October. Dead plants in the trial were not considered in the biweekly evaluation; thus, the ratings given only reflect the live plants. Members from the Perennial Trial subcommittee also evaluated and wrote comments for each plant variety in June, July, August and September. Plants and flowers were rated 0-5 using the following scale:

0 = Dead/No flowers

1 = Poor: Plants are very sick or dying, extremely few flowers

2 = Below Average: Plants are unattractive in some form, i.e. leggy growth habit, chlorotic or low vigor, flowers are few and occurring sporadically

3 = Average: Plant appearance with growth characteristics that would be expected for the time of season; flowers would be few but uniform across the plants

4 = Good: Plants look attractive (foliage, growth habit, etc.); flowers are blooming strong and showy

5 = Excellent: Plants are very healthy and uniform; flowering is impressive

Selection of ‘Top Performers’

On Nov. 16, 2018, a conference call was convened with CSU staff and the Perennial Trial Garden Subcommittee. Pictures of entries from the 2016 planting were posted to the Perennial Trial website for review. Data from the growing season was compiled and emailed to each evaluator prior to the conference call for review. After discussion and looking at the pictures taken throughout the season, each plant was voted on by each member of the committee as to whether it should be awarded the designation as a “Top Performer.”

‘Top Performer’ Perennials from the 2018 CSU Perennial Trial

Geum ‘RUSTICO™ Orange’ from Terra Nova® Nurseries
(Geum x ‘TNGEURO’PP28238)

Flowers were a beautiful bright orange and very prolific but the foliage was equally impressive, if not more so, and some evaluators commented the plant “looked so good that it didn’t even need the flowers.” Plants had a great dark-green foliage that kept a fresh look all through the season and made a good contrast for the colorful blooms. The growth habit was very controlled and had a very uniform appearance. It would make a great choice for mass plantings.

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 Flame® New Improved Purple from Dummen Orange®
(Phlox paniculata Flame® New Improved Purple)

Abundant purple flowers made a solid canopy of color at peak bloom, and also rated higher than other phlox for an impressively long bloom period. Plants had a very uniform growth habit with dark-green foliage. A small splash of white at the base of each petal added a bit of “sparkle” to each flower as it matured. Blooms also were noted to have an attractive color even as they faded late in season. Plants had superior resistance to powdery mildew.

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KISMET™ Raspberry Coneflower from Terra Nova® Nurseries

(Echinacea ‘TNECHKR’PP28768)

Prolific flowers formed a solid canopy of blooms over the plants and even had an attractive rustic look as it faded from peak bloom. Dark-green foliage kept the plant attractive even at times when the flowers were not present. Plants had a very uniform growth habit and good branching. The KISMET™ series also features colors of orange, red and yellow.

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Gaillardia ‘SpinTop Yellow Touch’ from Dummen Orange®
(Gaillardia aristata ‘SpinTop Yellow Touch’)

Plants were unique with a relatively small, compact-mounded growth habit but packed a lot of flower power on the top of each one. Flowers were very showy and predominately red but had an edge of yellow around the tip of each blossom. Plants had attractive green foliage that complemented the bloom color. Cold hardiness was also very impressive as the survival rate was very good for a Gaillardia. Additional entries in the ‘SpinTop’ series seemed to have superior cold hardiness as well.

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Delosperma ‘Alan’s Apricot’ from Plant Select
(Delosperma ‘Alan’s Apricot’PPAF)

Flowers made this a standout for both the unique color and continual blooming through the season. At peak bloom, plants are just a carpet of apricot-colored flowers. Plants are very uniform, have great vigor and have better cold hardiness than most Delosperma.  Good for low-water plantings, but will also tolerate extra water in areas that often kills other Delosperma. This is a great low maintenance plant.

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