CSU Perennial Trials 2015

Posted by: Jim Klett, Professor and Landscape Horticulture Extension Specialist

The herbaceous perennial trials continued in 2015 at Colorado State University. The trials are located at 1400 Remington Street adjacent to Annual Trial Gardens and University Center for the Arts.  These plants are trialed for three growing seasons and two winters. Twelve different companies from around the world entered 103 taxa in 2015.  There were a total of 211 different taxa of herbaceous perennials in the trial. The 2013 entries were evaluated for three years twice a month during the growing season and photographs taken at each evaluation.  Photographs from all dates were reviewed at the end of 2015 season to determine these “Top Performers”.

2015 CSU “Top Performers”

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. 

Electric Avenue coreopsis in landscape

Flowers of Electric Avenue coreopsis

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.
 

Beyond Blue fescue

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. 

Maestro hellebore flowers

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.

Merlin hellebore flowers

Merlin hellebore plant

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. 

Snow Fever 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. 

Little Lace Russian sage

Little Lace Russian sage, a compact version of the straight species

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. 

Sunrosa red rose

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. 

Dark Blue Moody Blues veronica

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. 

Pink Moody Blues veronica

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. 

Alexanders Great brunnera

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.

Forever Purple coral bells

Forever Purple coral bell leaf