Winter Color Trial Report

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
Top 10
Best of Breed
Leaders of the Pack
Early Season Leaders of the Pack
Late Season Leaders of the Pack
Cultivar Series Summaries
Weekly Ratings

Top Ten

Photographs below taken on March 31, two days after a low of 22°F.

Viola cornuta (Penny Primrose Blotch)

Viola cornuta (ColorMax Yellow Jump Up)

Viola cornuta (Endurio® Pure Yellow)

Viola cornuta (ColorMax Type Rosy White SM7-647)

Viola ×wittrockiana (Wonderfall™ Blue with Blotch)

Viola cornuta Endurio™ Sky Blue Martien

Viola cornuta (14CS01 Red with Yellow) (not photographed*)

Viola ×wittrockiana (Matrix Denim) (not photographed*)

Viola ×wittrockiana (Karma® Blue Sun) (not photographed*)

Viola ×wittrockiana (Wonderfall™ Purple with Face)

Viola cornuta (ColorMax Clear Purple)

Viola ×wittrockiana (Wonderfall™ Yellow)

Viola cornuta (ColorMax Purple Glow)

Viola ×wittrockiana (Wonderfall™ Lavender Picotee Shades)

Viola cornuta (Sorbet XP Yesterday, Today, Tomorrow)

Viola cornuta (Sorbet XPLavender Pink) (not photographed*)

Viola ×wittrockiana (Delta Premium Neon Violet Improved) (not photographed*)

Viola cornuta (Penny Deep Marina Improved)

Viola cornuta (ColorMax Type Yellow with Blotch SM0-600)

*Due to the March 29 late spring freeze, many flowers died. Flowering resumed within days.

General Introductory Notes and Acknowledgements

The Trial Gardens for seasonal color plant materials are located at NC State University within the JC Raulston Arboretum (JCRA) in Raleigh. The JCRA is an 10.5 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 feet.

Plants to be entered into our trials are received in a variety of ways. About half are germinated from seeds while the remainder originate as rooted cuttings or established cell plugs. Virtually all are grown within controlled greenhouse environments prior to placement in protected outdoor structures for hardening off. They were planted into their permanent trial bed locations on October 21, 2014. The predominant plant spacing in the trials was 18 inches × 12 inches (in-row × between-row spacing). Seven plants of each entry were used to evaluate landscape performance and ratings were taken weekly.


We thank the following for their support of material donations this season:

  • Campbell Road Nursery, 2500 Campbell Road, Raleigh, NC 27606
  • SunGro Horticulture, 3723 Hogshead Road, Apopka, FL 32702

We are especially thankful to the volunteers of the JC Raulston Arboretum who assisted in planting and maintaining the beds. We couldn't have done it without you!

Understanding Our Data

Number of Weeks in Flower

This is recorded as the total number of weeks in flower throughout the entire season. It should give you an idea of whether or not a plant is best used for the whole season or as a "fill-in" for special displays. Obviously, those species grown for foliage interest alone, e.g. ornamental kale, may score poorly in this column and should not be rejected based on this value alone!

Weekly Ratings

Plants were given a visual rating weekly by the same person beginning November 21, 2014, (about three weeks after planting) through March 31, 2015. 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.

Summaries of Weekly Ratings

The first statistic that readers see is likely the "all season average." This value represents overall performance for the entire season. However, realizing that there are many species/cultivars which may do better in one part of the growing season versus another, we also provide an "early season average" and "late season average" for each entry. The former is the average of the first half of the evaluation period and the latter represents the end of the season. This information may be useful in planning short term plantings with high impact as well as for studying temperature preferences, life cycle changes, and/or the impact of photoperiod on plant performance. The "number of weeks rated above 3" gives you an idea of how consistently throughout the season an entry is an exemplary performer.

The Lists You'll Find In This Report

• "The Top 10" - this list shows the species/cultivars with the top ten "All Season Averages." These were our best overall performers. When the list exceeds ten, there were ties.

• "Leaders of the Pack" – lists all species/cultivars with an "All Season Average" of 3.5 or better. We consider this the arbitrary cutoff rating for a "significant performer" in Raleigh. This list shows all your best choices for planting, listed by plant name.

• "Leaders of the Pack – Early Season" – this shows entries with "Early Season Averages" of 3.5 or better based on the first half of the evaluations. This group may prefer warmer temperatures or only have a relatively short ornamental life, and might not show up on the "Leaders of the Pack" list above.

• "Leaders of the Pack – Late Season" – this shows entries with "Late Season Averages" of 3.5 or better based on the end of the season evaluations. They may prefer warm temperatures or flower as daylengths start to lengthen, again sometimes precluding them from inclusion on the overall "Leaders of the Pack" list.

• "Best of Breed" shows the best performing cultivars in each species.

• "Summary by Series" groups the information for cultivar series where appropriate. This can be a quick reference for related cultivars as well as a handy tool to judge the general performance of an entire series offered by a breeder/company.

• "Weekly Ratings" evaluation given for each entry on a weekly basis.

The Average Monthly Temperature and Precipitation for the Winter 2014–2015 Trials

Temperature 2014-2015 Graph

Precipitation 2014-2015 Graph

Our winter was much colder than normal with the second half of February being the coldest on record. In February, we had lows that bottomed out around 7°F, normally unheard of for our area. And we concluded the season with a late season blast (3/29/2015) with a low of 22°F! Our precipitation in the first three months of the season was slightly above average but in the last three months there was a significant decrease. We ended the season with a precipitation deficit of 1.2".


Variance: The Best of Uniformity

Sometimes I think that the one number most often overlooked in our report is the variance. Go to the "Leaders of the Pack" data tables and look for its column. The term itself may be intimidating in light of its mystery, but need not be as it can be most informative. Simply put, the lower the variance, the most alike all plants are in the group evaluated, and hence the greater the uniformity. For so many in the commercial landscaping sector, they live and die by uniformity because appearance can be everything. So, by using a selected variance value of 0.1 as our very tough cut-off, we can really see which plants are setting the standard for superb uniformity.

Variance: All Over the Page

Whereas small variance values indicate excellent uniformity, the opposite can point out cultivars with a "mind of their own!" They are not necessarily a poor choice, just not ruler perfect. In this case, plants with variance values of 1.0 or more were highlighted for great differences observed during the season.

Seed and Plant Material Sources

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

  • All-America Selections, 1311 Butterfield Road, Suite 310, Downers Grove, IL 60515-5606
  • PanAmerican Seed, 622 Town Road, West Chicago, IL 60185
  • Sakata Seed America, 18095 Serene Drive, Morgan Hill, CA 95037
  • Syngenta Flowers, 6899 Winchester Circle, Suite 102, Boulder, CO 80301