Perennial Trials reveal top 5 performers in Rocky Mountain conditions


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 the planting and maintenance of 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 on a bi-weekly basis from May to early October. Dead plants in the trial were not considered in the bi-weekly 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. 

“Top Performer” Perennials from the 2020 CSU Perennial Trial
1. Allium ‘Summer Beauty’ (Allium lusitanicum) from Stonehouse Nursery, LLC: Soft lavender blue flowers were prolific and brought strong flower power later in the summer. Flowers were relatively tall and held above foliage for maximum show but had good structure and did not lodge. Plant were uniform and very attractive with glossy, green flat leaf blades.

2. Echinacea ‘Sombrero Tres Amigos’ (Echinacea x hybrida) from Darwin Perennials: Flowers were unique with an “evolution of color” that resulted in about three different shades of color during the season. Blooms were vibrant with a rich saturated color. Abundant flowers remained in bloom a long time and created an impressive overall show. Plants had a good growth habit with strong branching and no disease.

3. Penstemon ‘Dakota  Burgundy’ (Penstemon digitalis) from Terra Nova Nurseries: Dark burgundy foliage was a key reason for the superior rating. Multiple shades of burgundy added interest to the dark foliage and help make the white/lavender flower color really stand out. Blooms are very prolific with a long flowering period. It was noted that although the flowers are very impressive, the plant looks very showy even when not in flower due to the attractive dark foliage that remained clean all season and never had got “floppy ear”. Plants were very reliable and had 100% survival over three seasons.

4. Phlox ‘Ka-Pow’ series (Phlox paniculata) from Darwin Perennials:
Evaluators were impressed with the entire series as all had similar height, were very uniform and resistant to powdery mildew. Flowers had a long period of bloom with no color fade. Series had a range of colors that went from soft lavender to a vibrant pink. The pink entry was noted to have some shades of coral which is unique to Phlox.

5. Salvia ‘Blue by You’ (Salvia nemerosa) from Darwin Perennials:
Vibrant blue flowers were very showy with prolific amounts of blooms early in the season and an impressive repeat later in the season after a hard cut back of old blooms. The unique blue color is a great addition to the pallet of Salvia colors in the trade and evaluators said they “had to go see it” from across the garden.

Read the complete research at



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