Perennials Trial Report

North Carolina State University
Raleigh, North Carolina

JC Raulston Arboretum at
North Carolina State University
Raleigh, North Carolina

Mark Weathington

Bernadette Clark
Agricultural Research Technician

Department of Horticultural Science
JC Raulston Arboretum

Table of Contents

General Introductory Notes and Acknowledgements
Understanding Our Data
Climate Graphs
Plant Material Sources

General Introductory Notes and Acknowledgements

The Perennials Trial are located adjacent to the Color Trials at NC State University within the JC Raulston Arboretum (JCRA) in Raleigh. The JCRA is a ten and a half acre site administered by the Department of Horticultural Science and located on 35° 47'N latitude, longitude 78° 42' W, with an elevation of 400'.

Plants to be entered into our trials are received in one of three ways—seeds, rooted cuttings/plugs or finished plants/pot. Virtually all are grown within controlled greenhouse environments prior to placement in protected outdoor structures for hardening off. Plant spacing in the trials is based on the estimated mature size of entrant that fits to a 4' × 4' area or by the number of plants sent. Each entry is evaluated for two complete calendar years, being removed after the spring flush in year three. After the plants are established, they are evaluated for hardiness and landscape performance with ratings regularly taken.


We thank the vegetative and seed companies that participate in our trials. The services we provide would not be possible without the cooperation and support of these companies. We appreciate this confidence and trust and we look forward to continuing our partnership.

Lastly, we are thankful to other departmental staff and the volunteers of the JC Raulston Arboretum who assisted in transplanting and maintaining the plants … we couldn't have done it without you all!



Dümmen Orange
Syngenta Flowers
Walters Gardens, Inc.


Dümmen Orange
Syngenta Flowers

We also thank the following companies for their support of material donations:

  • BASF, 26 Davis Drive, Research Triangle Park, NC 27709
  • Sun Gro Horticulture, 3723 Hogshead Road, Apopka, FL 32702

Understanding Our Data

Cultural Data

Trials are conducted in amended beds. Prior to planting, beds are fertilized with 10-10-10 granular fertilizer and tilled. All plant material is mulched with composted leaf mulch to a 2"–3" depth after planting. Pre-emergent herbicides are used at the initial planting and repeated each subsequent spring/summer season. Hand weeding is done at all other times. Later in the season, a post-emergent herbicide application along the edge of the beds was done on an as needed basis. An in-ground irrigation system delivers 1"–1.5" of water to the beds each week. Plant height and width measurements (recorded in inches) are taken during the growing season. Data was collected from a representative plant, not the largest or the smallest but an average plant. Dormant plants were cut back in the fall/early winter to clean up the area and reduce overwintering habitat for insects and diseases.


The purpose of our perennials trial is to evaluate the plant material under conditions unique to our location. Our summer growing conditions are typically hot temperatures with high humidity. There is little nighttime temperature relief/recovery; average summer nighttime temperatures can be in the 70s. Irrigation is required all season.

Plants were given a visual rating by the same person. The overall rating was based on plant performance and appearance, including floriferousness, plant size and shape, and freedom from insect and disease problems. The rating scale ranged from 1 (very poor) to 5 (excellent) with 0.5 unit increments possible; a 0 rating indicated that all plants of the cultivar trial died.

What do we look for?

  • General Plant Growth – healthy appearance, attractive foliage, uniform growth
  • Flowers – floriferousness, bloom duration, uniform color, does it hold up after a heavy rain
  • Pests and diseases – any visible evidence of damage: distorted or chewed foliage
  • Heat tolerance – do the flowers and plants hold up in the heat, does the flower color fade or stripe
  • Hardiness (survival) – determined (in the spring) by the number of plants that made it through or emerged after the winter

Installation Date

Most entries were planted into their permanent trial location on:

  • 2014 entries on May 13, 2014
  • 2015 entries on May 12, 2015, and October 20, 2015

Entries that Did Not Survive

Died 2014

Heuchera 'Dolce Cinnamon Curls'
Lavandula angustifolia
'Sweet Romance'
Nepeta 'Cat's Meow'
Penstemon 'Arabesque Appleblossom'
Penstemon 'Arabesque Pink'
Penstemon 'Arabesque Red'
Penstemon 'Arabesque Violet
Phlox paniculata 'Early Dark Pink'
Phlox paniculata 'Early Purple'

Died 2015

Aubrieta 'Audrey Deep Blue Shades'
'Audrey Red'
'Pearl Deep Blue'
'Pearl White'
Dianthus 'Odessa Orange Bling Bling'
Dianthus 'Odessa Easy Pink'
Lavendula 'Blue Scent Improved'
Lavenudula 'White Scent Early'
Penstemon 'Experiemental Arabesque Magenta'
Penstemon 'Experimental Red Dwarf'
Penstemon 'Experimental Violet Dwarf'
Salvia 'Salute IceBlue'

The best way to really evaluate our trials is to come in person. The JCRA is open 365 days a year.

Average Monthly Precipitation and Temperature

Precipitation Graph - 2011-2014

Temperature Grpah- 2011-2014

Cool spring temperatures (2015) led to slightly warmer than normal summer temperatures. In June, we experienced a 16-day period of temperatures at 95°F or above. The hottest temperature (102°F) occurred on June 16. The total number of days at or above 90 was 58, roughly 38% of our growing period. It was very humid, according to the meteorologists, the most humid summer in 20 years. The heaviest rainfall, which was 2.0", occurred on June 19. Rain totals for the summer season exceeded the norm by 3.65".

The winter season (2015–2016) was hard on the plants. In October and November, the temperatures were slightly warmer than normal but December was downright warm. The average daily temperatures during December were 12° higher than our normal (55.4°F vs. 42.8°F). On November 22, the first freezing event occurred, with a low temperature of 26°F.

Our cold period began in January. Our average night temperature for December was on par with the daytime highs of January and February. Even though the temperatures were in our normal range for both January and February, the plants were not well acclimated. Our coldest night, 15°F, was on February 14. We had relief in March with the return of warmer temperatures; the average daily temperature during March was 7°F higher than normal (57.3°F vs. 50.5°F).

Our precipitation in October, November, December, and February greatly exceeded (10.4") our normal amounts. Both January and March were below average. We ended the season with an excess of 8.8".

Seed and Plant Material Sources

Benary, 267 Osprey Drive, Pell City, Alabama, 35128
Dümmen Orange, 15245 W. Telegraph Road, Santa Paula, CA 93060
Syngenta Flowers, 6899 Winchester Circle, Suite 102, Boulder, CO 80301
Walters Gardens, Inc.
, 1992 96th Avenue, Zeeland, MI 49464

Please get in touch with these companies if you have specific questions regarding individual species and cultivars.

Trial Results

Perennials Planted in 2014

Perennials Planted in 2015