Perennial Trials reveal top 9 performers in Rocky Mountain conditions

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

Evaluating perennials in the Rocky Mountains

Nearly 40 years ago, Colorado State University established trial gardens prepared to evaluate annual selections. In 2007, perennial trials were creat­ed adjacent to the annual flower trials in response to increased inter­est in new perennial cultivars.

The purpose of the trial garden is to evaluate 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.

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 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 Trial Garden receives no direct 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 came and wrote comments for each plant 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 November 16, 2015, a conference call was convened with CSU staff and the Perennial Trial Garden Subcommittee. Pictures of entries from the 2013 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”.

Electric Avenue Coreopsis from Creek Hill/Eason (Coreopsis verticillata ‘Mayo Clinic Flower of Hope’PPAF or ‘Electric Avenue’)
Bright yellow flowers covered the plants over a very long bloom period . Plants were sturdy, compact and uniform from spring to fall. Fine textured foliage and a nice flower shape contributed to a very pleasing overall affect. Overwintering survival was impressive both years
compared to many other Coreopsis in trial.  This was designated as a winner of the “Too Good To Wait” award in 2014 and did not disappoint in 2015 either.

Beyond Blue Fescue from Skagit Gardens (Festuca glauca ‘Casca11’ PP #23307 )
This fescue was considered to have the best “blue” color out there! Plants maintained a nice “ball” shape and did not open in the middle. Plants were very uniform even after two hard winters and three growing seasons.  Flower stems were very few in 2015 and faded into foliage for a superior appearance. This is an improved variety over older ones for foliage color.  This was designated as a winner of the “Too Good To Wait” award in 2014 and did not disappoint in 2015 either.

Gold Collection® Maestro Hellebore from Skagit Gardens (Helleborus x ballardiae  ‘COSEH 890′)
Shiny, dark green foliage appeared almost black at times towards the end of the season.  Flowers petals emerge a deep pink with white and mature to a creamy white with shades of dusty rose on the back side.   Flowers covered the plant from side to side and were very prolific.  Plants were compact and with good vigor.

Gold Collection® Merlin Hellebore from Skagit Gardens (Helleborus x ballardiae  ‘COSEH 810’USPP #22350 )
Flowers emerged with pink color that is brighter than most and then matured to shades of dusty rose.  Blooms were held above foliage creating an impressive display.  Plants were more compact with long lasting dark green foliage and very low maintenance.

Gold Collection® Snow Fever Hellebore from Skagit Gardens (Helleborus x argutifolius ‘COSEH900’PPAF )
The speckled green and white foliage makes this a great foliage plant that will add sparkle in shady areas even when not in flower.  Sturdy plants have proven hardy over two winters that have been too severe for other variegated varieties of Hellebore.

Little Lace™ Russian Sage from Star Roses and Plants/The Conard-Pyle Co. (Perovskia ‘Novaperlac’)
Growth habit is unique as it combined a shorter plant with great uniformity.  Purple flower spikes were long lasting and created a lot of flower power.  The tidy, compact plants were a significant improvement over typical sprawling Russian sage in general.  It makes a good choice for xeric areas.

Sunrosa™ Red Rose from Suntory® Flowers (Rosa x hybrid Sunrosa™ Red)
Constant red flowers and impressive growth habit made this plant attractive all season. Glossy dark green foliage had no signs of chlorosis or disease. Red flowers did not fade and bloomed steadily from mid-June through October. Small foliage and a dwarf compact growth habit made this a good choice for the smaller or mid-size landscapes. The compact growth habit is maintained without any pruning.  This was designated as a winner of the “Too Good To Wait” award in 2014 and did not disappoint in 2015 either.

Dark Blue Moody Blues™ Veronica from Star Roses and Plants/The Conard-Pyle Co. (Veronica ‘Novaverblu’)
Long bloom period and the abundant spikes of dark blue flowers made this a standout.  Plants were very uniform and had excellent winter hardiness.  Additionally, plants had good resistance to disease and there was no signs of powdery mildew.  The entire Moody Blues™ series was noted for superior performance.

Pink Moody Blues™ Veronica from Star Roses and Plants/The Conard-Pyle Co. (Veronica ‘Novaverpin’)
Flowers were noted for having exceptionally uniform, perfect spikes of light pink flowers that helped create an impressive overall display.  Growth habit and flowering were very uniform.  The overall height was taller than others in the Moody Blues™ series but still maintained a nice compact habit.  The entire Moody Blues™ series was noted for superior performance.

Class of 2014 – “Too Good to Wait”

The Perennial Trial Committee likes to award ‘Top Performer’ to plants that have been in the ground 2 winters and 3 growing seasons. This category is to acknowledge an upcoming plant that has been in the ground one winter and two growing seasons and has shown excellent performance thus far in the trial. The following two plants impressed the Perennial Trial Committee so much that they designated the category name: “Too Good to Wait Performer”.

Alexanders Great Brunnera from Terra Nova Nurseries, Inc. (Brunnera macrophylla ‘Alexanders Great’ PP25,789)
This is a unique Brunnera of “monster” growth proportions which is an excellent choice to add structure to the garden.  The large size also helped show off the heavily silvered leaves resulting in a dramatic statement for the garden.  It makes a great foliage plant for shady areas but also had a good display of blue flowers that created a light, airy appearance.

Forever Purple Coral Bells from Terra Nova Nurseries (Heuchera ‘Forever Purple’PPAF)
Leaves had an intense purple color with a shade of red was maintained all season.  The glossy foliage seemed to make the color “bounce” off the leaf.  It is grown mostly for attractive foliage which also has fluted edges.   Plants had good vigor and a uniform growth habit.