Summer Color Trials Report

North Carolina State University
Raleigh, North Carolina
2024

Mark Weathington
Director

Bernadette Clark
Agricultural Research Technician

Department of Horticultural Science
JC Raulston Arboretum

Table of Contents

• Top Performers
• General Introductory Notes and Acknowledgements
• Understanding Our Data
• Climate Graphs
• Variance
• Plant Material Sources
• Reports
  • 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

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 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 a variety of ways. About one quarter 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 May 13, 2024 and containers on May 21, 2024. The predominant plant spacing in the bed trials was 18" × 24" (in-row × between-row spacing). Seven plants of each entry were used to evaluate landscape performance. Hanging baskets and containers had one plant each and were replicated three times. All ratings were taken weekly.

Acknowledgements

We thank the following for their support:

• BASF, 26 Davis Drive, Research Triangle Park, NC 27709
• Pacific Organics, 650 Peter Gill Road, Henderson, NC 27537

We are especially thankful to the departmental staff and the volunteers of the JC Raulston Arboretum who assisted in transplanting and maintaining the annual beds throughout the growing season … we couldn't have done it without you all!

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. Acalypha, 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 May 29, 2024 (about two weeks after planting) through October 02, 2024. 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.

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

Summaries of Weekly Ratings

The first statistic that readers run to is likely the "all season average." This value represents overall performance for the entire summer 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 data is presented in three categories: beds, containers, and hanging baskets. This allows a truer, more equitable way of comparing the entries. Each category will have the individual breakout of data, just like before. For example, you will be able to view a Top 10 listing for beds, containers, and hanging baskets entries.

"The Top 10" (beds, containers, and hanging baskets) – 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" (beds, containers, and hanging baskets) – 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" (beds, containers, and hanging baskets) – this shows entries with "Early Season Averages" of 3.5 or better based on the first half of the evaluation period. This group may prefer cooler 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" (beds, and containers) – this shows entries with "Late Season Averages" of 3.5 or better based on the end of the season evaluations. They may prefer very warm temperatures or flower as daylengths start to shorten, again sometimes precluding them from inclusion on the overall "Leaders of the Pack" list.

"Best of Breed" (beds containers, and hanging baskets) – shows the best performing cultivars in each species.

"Summary by Series" (beds, containers, and hanging baskets) – 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" (beds, containers, and hanging baskets) – evaluation given for each entry on a weekly basis.

The Average Monthly Precipitation and Temperature for the Summer 2024 Trials

Our growing conditions this summer were all over the spectrum. May was slightly drier with "normal" temperatures. In June, we experienced the beginning of an extreme heat pattern. Two-thirds of the month had temperatures that exceeded 90℉ coupled with virtually no rain (0.46 inch). June 2024 was our second driest June on record. July continued the exceptional heat. We set a record breaking daily high temperature on July 5 (100℉). The heat index that day reached 118℉! July’s rainfall was above normal. The warm temperatures continued through August. Tropical Storm Debby brought much needed rain (4.53") over a two-day period the first half of the month. Unfortunately, we had no appreciable rainfall for the remainder of the August. We welcomed the more comfortable temperatures that September brought. An early-month storm dumped more than 4 inches of rain over a multi-day period. This heavy rain pattern continued through the entire month. September precipitation ended with an amazing 14.11" total!

Our greatest amounts of rainfall occurred on August 8 (2.68" ), September 1 (2.07" ) and September 16 (2.41" ). Our first 90-degree day occurred on May 21 (90℉). June had the most 90℉+ days at 19 days followed by July with 16 days. We had two 100℉+ days, July 5 (100℉) and July 6 (102℉).

These numbers do not adequately show the volatile weather conditions we experienced this summer. It was a summer of extremes, high heat matched with both extreme rainfall AND extreme drought. This was a difficult growing season for the plants.

Variance

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. In many cases our results have confirmed some excellent reputations, for others, it's a first time notice.

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. To be fair, there are many reasons for a lack of uniformity, most likely of which would simply be the result of our normal or extreme weather.

Seed and Plant Material Sources

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

Seed and Plant Material Sources

All-America Selections, 5201 Walnut Avenue, Suite 3, Downers Grove, IL 60515

Ball FloraPlant, 622 Town Road, West Chicago, IL 60185

Ernst Benary of America, 195 Paulsen Road, Watsonville, CA 95076

Danziger, Mishmar Hashiva, Israel

Known-You Seed American Corp., 26360 Ruether Ave., Santa Clarita, CA 91350

PanAmerican Seed, P.O. Box 335, West Chicago, IL 60185

Proven Winners, 1600 E. Lincoln Hwy Ste F, Dekalb, IL 60115-4962

Sakata Seed America, 18095 Serene Drive, Morgan Hill, CA 95037

Selecta One, P.O. Box 335, West Chicago, IL 60185

Suntory Flowers, 2907 Deer Run Rd., Brenham, TX 77833