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Hort. Series # 247

Principal Investigators: Jonathan R. Schultheis, Professor and Extension Specialist, Department of Horticultural Science, NC State University; Stuart W. Michel, Research Technician, Department of Horticultural Science, NC State University; Brandon K. Parker, Research Associate, Department of Horticultural Science, NC State University; Baker E. Stickley, Research Assistant, Department of Horticultural Science, NC State University.

                        View or print the pdf of this report

Acknowledgements

We gratefully acknowledge the assistance of Hunter Barrier (Superintendent) and Wesley Hairre (Horticulture Supervisor), Horticultural Crops Research Station, Clinton, NC, as well as the personnel at the research station for their help in establishing, maintaining, and harvesting the 2024 cultigen evaluation study. We want to acknowledge summer employees Lia Hunt, Daphne Meyer, Cameron Roberts, and Nathaniel Wyschka for their assistance with this study. The cooperation and support of BASF/Nunhems, Enza Zaden, Hazera, Known You Seed, Origene, Seminis, Seedway, Syngenta, and U.S. Agriseeds were also appreciated. We also want to thank Joy Smith for performing the statistical analysis and aiding in the interpretation of the data collected from this study.  

Financial Support

In addition to seed companies, this research was supported by the College of Life and Agricultural Sciences, North Carolina Agriculture Research, the North Carolina Cooperative Extension Services, and the North Carolina Department of Agriculture and Consumer Services. This work was in part supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2020-51181-32139 (CucCap).

Disclaimer

This publication presents data from the standard size triploid watermelon cultigen evaluation study conducted during 2024. Information in this report is believed to be reliable but should not be relied upon as a sole source of information. Limited accompanying detail is included but excludes some pertinent information, which may aid interpretation.

Introduction

Watermelon production in North Carolina totaled 9,600 acres harvested in 2023, a value of approximately $48.4 million. Acreage has increased from 7,600 acres in 2022, however the price per unit (cwt) has decreased from $23.80 in 2022 to $15.80 in 2023 (NC Ag Stats).

Nationally, consumer demand for whole standard watermelon has increased by 11.9% from 2022-23 to 2023-24. This year, whole standard watermelon accounted for 76.0% of all watermelon sales in the U.S. In the Southeast, whole standard watermelon demand increased 13.3%. This increase is reflected in the North Carolina market. Retail scanner data shows the Charlotte area had a 14.6% increase in sales, and the Raleigh/Greensboro area had a 13.3% increase in sales (2023 Watermelon Retail Scan Data).

In 2024, Dr. Schultheis and the Cultural Management Program in the Horticulture Department at NC State University conducted an evaluation of 29 standard size triploid (seedless) and 2 diploid (seeded) cultigens from 9 seed companies at the Horticultural Crops Research Station in Clinton, NC. The watermelon entries were evaluated for yield and quality characteristics such as soluble solids (sweetness or Brix), color, firmness, and hollow heart. The methods, results, and representative photos from the study are presented in the pages at the end of this report.

Materials and Methods

Sowing and Field Preparations

Once all seeds were received from participating companies, they were planted into 72-cell poly trays to grow transplants (Hummert Int.; Earth City, MO). The watermelons were sown on 25 March 2024. The trays of sown seeds were placed in a germination room for 24-48 hours. Temperature in the germination room was kept between 90-95°F and humidity was kept between 85-90%. The planting medium used was a ‘fine germinating mix’, a commercial soilless mix (SunGro, Agawam, MA). After germination, transplants were moved to a greenhouse set to 85°F and hand watered twice daily. The seedlings were fertilized at least once a week with 20-10-20 water soluble fertilizer at a rate of 200-250 ppm.

The field planting site was located at the Horticultural Crops Research Station in Clinton, NC. The standard watermelons were planted in block F1; a 2.2-acre field consisting of an Orangeburg loamy sand soil. Fertilizer (10-10-10-SOP) at 500 lb/ac was applied on 1 April 2024. Fertilizer (0-0-22-22-11Mg) at 150 lb/ac was applied on 4 April 2024. Pic 60 (6 gal/ac) was sprayed to fumigate the entire study area on 9 April 2024 for weed and nematode control. Black polyethylene plastic (1.25 mil thick, high density plastic film, 54 inches wide; TriEast Ag Group, Inc., Clinton, NC) was laid on 6 inch raised beds, 30 inches wide, on 9 April 2024.

Transplanting and Vine Training

The triploid (seedless) watermelon transplants were established in the field on 1 May 2024. Plot size for the standard size watermelons was 1 row, 10 plants per row, 25 feet long with alleys of 10 feet between plots. Row middles were 10 feet and in-row spacing was 2.5 feet. Plots with missing plants were replaced 7 days after transplanting to achieve 100% plant stand. ‘SP-7’ and ‘Wingman’ (4 plants/plot) were used as the pollenizer plants in this study. ‘SP-7’ pollenizers were planted after triploid plants 1 and 7 while ‘Wingman’ pollenizers were planted after triploid plants 4 and 10 in each plot. Once vines had grown over the plastic mulch, they were gently turned/trained back into the plot each week. This aided harvest by avoiding mixing cultigens and reducing vine damage at harvest.

Fertilizer and Pest Management

A total of 50 lb/ac N, 50 lb/ac P, 83 lb/ac K, 33 lb/ac Ca, and 16.5 lb/ac Mg were all applied broadcast (pre-plant) to the entire study area using granular fertilizers with analyses of 10-10-10 and 0-0-22-22-11. Drip tape (NETAFIM, 12 in spacing, 0.24 gph; NETAFIM, Tel Aviv, Israel) was installed beneath the black plastic mulch to fertigate the crop throughout the growing season. Liquid fertilizer with 4-0-8 analysis was applied through drip tape fertigation throughout the growing season at rates and times suggested by the fertigation schedule for watermelon in the Southeastern U.S. 2024 Vegetable Crop Handbook . Cumulative totals, pre-plant and through the drip tape, of applied fertilizer nutrients were: 136.9 lb/ac N, 50 lb/ac P, 256.8 lb/ac K, 33 lb/ac Ca, and 16.5 lb/ac Mg.

Herbicides (Table 1), insecticides (Table 2), and fungicides (Table 3) were applied as needed and as directed by the label for that crop (2024 NC Ag Chem Manual). Different products were rotated to avoid potential development of resistance.

Weather

Weather was not consistent during the growing season, as both flood and drought conditions occurred across North Carolina. A period of drought occurred in June, during which the field site received less than 1 inch of rain in 30 days (Figure 1). A tropical storm system then brought heavy rain in late July, resulting in flooding of plots and rotting of fruit on the vine and ultimately leading to only harvesting the study three times, compared to five harvests in 2023. A total of 17.5 inches of rain occurred at the field planting site in Clinton, NC throughout the duration of the study.

Study Design and Data Collection

The study used a randomized complete block design with four replications. There was a total of 3 harvests collected over 17 days (9 July through 25 July) with some harvests spanning 2-3 days. Fruits were picked when signs indicated they were ripe; yellow to tan ground spot, dead tendrils, ribbing, color. Fruits were counted and weighed individually. Fruit with pest damage and or rot were weighed and counted if the fruit was intact and representative of the rest of the plot. Vines were moved to cover unpicked fruit to minimize the occurrence of sunscald at later harvests.

Quality Evaluations

Measurements were taken on 12 fruit (3 per replication) of each cultigen to determine the fruit size, fruit shape, soluble solids (sweetness or Brix), interior flesh firmness, flesh color, rind thickness, seed trace size, hard seed population, and hollowheart. The most representative fruit were selected for quality measurements and measurements were retaken on another fruit if necessary. Soluble solids were measured by cutting a piece of flesh from the center of the fruit and squeezing out the fruit juice onto the digital refractometer (Atago, Vernon Hills, IL). Flesh firmness was taken using a Penetrometer FT 011 with a 7/16’ plunger tip (QA Supplies LLC, Norfolk, VA), and was recorded in pounds. Samples were obtained by cutting the center of the fruit from the stem to blossom end. Pressure was then taken in five areas of the fruit: stem end, top side, ground spot side, blossom end, and center. The reported measures on flesh firmness are an average of the five sample areas; pressure was not taken on fruit with hollowheart. Hard seed in triploid fruit was determined according to the USDA standards. Fruits were cut longitudinally in half, and then the halves were cut laterally. The number of hard seeds exposed on the cut surface were counted and recorded. Most of the quality measurements were taken in the first harvests (1-2). Additional information on the quality measurements is presented in the Quality section on page 9 and in Table 8.

Results and Discussion

A period of drought in the early season followed by heavy rains in July resulted in lower yields and fewer harvests in this year’s study, which is indicative of many watermelon growers in North Carolina this year.

For the analysis, fruits were placed in the following size categories: < 9 lb, 9-13.4 lb (60-count bins), 13.5-17.4 lb (45-count bins), 17.5-21.4 lb (36-count bins), and ≥ 21.5 lb (30-count bins). The yellow flesh cultigen ‘Buttercup’ from Seedway as well as two popular red flesh cultigens, ‘Fascination’ from Syngenta and ‘Cracker Jack’ from Enza Zaden, were included as comparisons.

Cumulative Harvests (1-3)

Yield: Cwt per acre

The cultigen ‘Essence’ from Origene had the highest marketable yield of all 31 entries in this study at 513 hundred-weight per acre (cwt/ac) (Table 4). ‘ORS 61229’ from Origene had the second highest marketable yield at 468 cwt/ac. The average marketable yield across all 31 cultigens was 369 cwt/ac. Popular cultigens ‘Cracker Jack’ and ‘Fascination’ had marketable yields of 412 cwt/ac and 385 cwt/ac, and were ranked ninth and twelfth, respectively. Most of the yield in this study fell into the 9-13.4 and 13.5-17.4 lb categories. ‘Essence’ differed statistically in marketable yield with entries ‘Tropical Sunshine’, ‘Marshall’ and ‘Nun 32206’ (Table 4).

Yield: Number of fruit per acre and number of fruit per plant

‘Buttercup’ from Seedway had the highest number of marketable fruit per acre (Mkt no/ac) at 3180 (Table 5). ‘Essence’, ‘ORS 61229’, and ‘ORS 61421’ from Origene were tied for the second highest number of marketable fruit per acre at 3093. The average number of marketable fruit per acre across all entries was 2517. ‘Cracker Jack’ and ‘Fascination’ had 2875 and 2657 marketable fruit per acre, and were ranked third and seventh, respectively.

‘Buttercup’ from Seedway had the highest number of fruit per plant (Fruit no/plant) at 2.3 (Table 5). ‘Tropical Sunshine’ from Seedway and ‘Nun 32206’ from BASF/Nunhems were tied for the second highest number of fruit per plant at 2.2 but ranked fifteenth and nineteenth for marketable number per acre, respectively. The average number of fruit per plant across all entries was 1.7.

Yield: Bins per acre

‘Essence’ from Origene was the entry with the highest number of bins with marketable fruit per acre (Mkt bins/acre) across all entries with 73 bins (Table 6). Marketable bins does not include fruit in the less than 9 pound category (< 9 lb). ‘ORS 61229’ from Origene had the second highest number of marketable bins per acre at 67 bins. The average number of marketable bins across all entries was 53 bins. Cultigens ‘Cracker Jack’ and ‘Fascination’ had 59 and 55 bins with marketable fruit per acre and were ranked sixth and ninth, respectively.

Yield: Average fruit size and bin size distribution

The two diploid (seeded) cultigens from BASF/Nunhems, ‘Nun 22104’ and ‘Nun 22102’, produced the largest fruits in the study, ranking first and second at 19.4 and 18.8 pounds per fruit, respectively (Table 7). The triploid (seedless) cultigen with the largest fruit size was ‘Sweet Pontoon’ from Seminis at 17.8 pounds per fruit. ‘Sweet Pontoon’ had 80% of its fruit in the 30 and 36-count bin categories. The average fruit weight across all 31 entries was 14.0 pounds with a range of 19.4 to 8.7 pounds per fruit. Cultigens ‘Fascination’ and ‘Cracker Jack’ had average fruit weights of 14.1 and 14.0 pounds per fruit, and were ranked eleventh and twelfth, respectively.

‘Sweet Pontoon’ also had the highest percentage of fruit in the 30-count bin category at 44% along with ‘Nun 22104’ at 45% (Table 7). ‘53021’ from Hazera had the highest percentage of fruit in the 36-count bin category at 37%. ‘Cracker Jack’ from Enza Zaden had the highest percentage of fruit in the 45-count bin categories.

Quality

‘Sugar Treat’ from US Agriseeds, ‘ORS 61438’ from Origene, and ‘53016’ from Hazera were the sweetest of all 31 entries, all with an average Brix of 12.1 (Table 8). Brix is a measure of sugar content, and the units equate to 1 gram of sucrose in 100 grams of solution. ‘Black Jack’ from Seedway, ‘Cracker Jack’ from Enza Zaden, and ‘Essence’ from Origene all ranked second for sweetness with an average Brix of 12.0. The average sugar content across all 31 entries was 11.5, with the majority of entries having an average Brix above 11.0.

The entry with the firmest flesh was ‘Cato’ from Syngenta, with an average firmness of 3.9 pounds (Table 8). Cultigens ‘Cracker Jack’ and ‘Fascination’ had average flesh firmness ratings of 2.2 and 2.3 pounds, respectively.

‘ORS 61421’ and ‘ORS 61229’ from Origene had the highest flesh color ratings of all 31 entries with an average color rating of 4.9 for both entries; color is based on a 1 to 5 scale with 1 being pale or white and 5 being a deep blood red (Table 8). Flesh color was good in this study, with an average color rating of 4.5.

‘Valor’ from Syngenta had the thinnest rind at 9.2 mm (Table 8). ‘Nun 32002’ from BASF/Nunhems had the thickest rind at 14.5 mm. The average rind thickness across all cultigens was 12.2 mm.

‘Big Jack’ from Enza Zaden and ‘Buttercup’ from Seedway had the lowest population of hard seeds with an average 0.2 hard seeds per fruit (Table 8). ‘53022’ from Hazera had the highest population of hard seeds at 2.3 seeds per fruit, and the average across all cultigens was 0.7 hard seeds per fruit. All entries had minimal hard seeds.

‘Paddleboat’, ‘Sandbar (SVWA7826)’, and ‘Sweet Pontoon’ from Seminis, ‘Fascination’ from Syngenta, ‘Tropical Apollo’ from Seedway, ‘Rio Grande’ from Enza Zaden, and ‘ORS 61438’ from Origene all had the smallest seed trace in the study at a rating of 1.1; seed trace was measured on a 1-5 scale with 1 being small and 5 being large (Table 8). Overall, seed trace size was small across all entries with an average rating of 1.4.

Quality: Hollowheart

Over half of the cultigens in this study (19 out of 31) had no incidence of hollowheart (Table 9). Of those that did have hollowheart, only four cultigens had any fruit with a rating of 3 or higher; a rating of 3 or 4 are considered unmarketable.

Early Harvest (1): 9 and 11 July

Early Yield: Cwt per acre

‘ORS 61229’ from Origene had the highest marketable yield in the early harvest with 364 cwt/ac (Table 10). ‘Rio Grande’ and ‘Cracker Jack’ from Enza Zaden were ranked second and sixth with 354 and 322 cwt/ac, respectively. The average marketable yield for the early harvest was 268 cwt/ac. ‘ORS 61229’ and ‘Rio Grande’ differed statistically in marketable yield in the early harvest with ‘Amaltea’, ‘53016’, ‘Marshall’, and ‘Nun 32206’ (Table 10).

Early Yield: Number of fruit per acre and number of fruit per plant

‘ORS 61229’ from Origene had the highest number of marketable fruit per acre (Mkt no/ac) at 2483 (Table 11). ‘Powerhouse’ from Syngenta and ‘Tropical Sunshine’ from Seedway had the highest number of fruit per plant (Fruit no/plant) at 1.6 for the early harvest. ‘Powerhouse’ and ‘Rio Grande’ from Enza Zaden had the second highest number of marketable fruit per acre, with both cultigens at 2309. The average number of marketable fruit across all entries was 1820 fruit per acre and the average number of fruit per plant was 1.2.

Early Yield: Bins per acre

‘ORS 61229’ from Origene, ‘Rio Grande’ from Enza Zaden, and ‘Virtue’ from Syngenta had the highest number of bins with marketable fruit per acre (Mkt. bins/ac) for the early harvest at 52, 51, and 50 bins/ac, respectively (Table 12). The average number of bins with marketable fruit per acre in the early harvest was 38 bins per acre. Most of the fruit fell into the 13.5-17.4 lb category.

Mid-Season Harvest (2): 17 and 18 July

Mid-Season Yield: Cwt per acre

‘Buttercup’, a yellow flesh cultigen from Seedway had the highest marketable yield for the mid-season harvest at 168 cwt/ac (Table 13). ‘Essence’ from Origene ranked second at 134 cwt/ac, and ‘Sugar Treat’ from US Agriseeds ranked third at 106 cwt/ac for the mid-season harvest. The average marketable yield across all entries was 69 cwt/ac for the mid-season harvest. Most of the yield for the mid-season harvest fell into the 9-13.4 lb size category. There were no statistical differences in marketable yield for this harvest time.

Mid-Season Yield: Number of fruit per acre

‘Buttercup’ from Seedway had the highest number of marketable fruit per acre for the mid-season harvests at 1350 (Table 14). ‘Amaltea’ from Seedway ranked second for marketable fruit per acre at 784 no/ac, and ‘Essence’ from Origene and ‘Sugar Treat’ from US Agriseeds both ranked third at 741 no/ac. The average number of marketable fruit across all entries for the mid-season harvest was 472 no/ac.

Mid-Season Yield: Bins per acre

‘Buttercup’ from Seedway had the highest number of bins with marketable fruit per acre for the mid-season harvest at 24 bins/ac (Table 15). ‘Essence’ from Origene had the second highest number of marketable bins in the mid-season at 19 bins/ac, while ‘Sugar Treat’ from US Agriseeds and ‘53022’ from Hazera both ranked third at 15 bins/ac. The average number of marketable bins across all entries in the mid-season harvest was 10 bins/ac.

Late Harvest (3): 25 July

Late Yield: Cwt per acre

‘Big Jack’ from Enza Zaden, ‘Essence’ from Origene, and ‘53016’ from Hazera had the highest marketable yields in the late harvest with 92, 88, and 72 cwt/ac, respectively (Table 16). The average marketable yield for the late harvest across all entries was 34 cwt/ac. There were no statistical differences in marketable yield for the late harvest.

Late Yield: Number of fruit per acre

‘Essence’ from Origene, ‘Big Jack’ from Enza Zaden, and ‘53016’ from Hazera had the highest numbers of marketable fruit per acre for the late harvest at 610, 566, and 523, respectively (Table 17). There were less fruit overall in the late harvest compared the early and mid-season harvests, with an average of 240 fruit per acre. Only the top three cultigens listed above yielded more than 400 fruit per acre in the late harvest, while the average across all entries in the mid-season harvest was 472 fruit per acre.

Late Yield: Bins per acre

‘Big Jack’ from Enza Zaden and ‘Essence’ from Origene had the highest number of bins with marketable fruit per acre for the late harvest, both at 13 bins/ac (Table 18). The average number of marketable bins per acre was 5 across all entries in the late harvest.

Perspective on New Cultigens

About one half of the entries in the 2024 North Carolina standard size watermelon cultigen study were evaluated for the first time. It is important to see consistency in yield and quality over a couple of growing seasons. However, based on favorable data and observations for the first-year entries, these cultigens made a good first year impression: Big Jack, Black Jack, ORS 61229, ORS 61421, Sandbar, Sugar Treat, Sweet Pontoon, and 53021. Yield and quality of these cultigens compared favorably to the most commonly grown cultigens in North Carolina, Fascination and Cracker Jack. These new cultigens should be assessed over multiple years or seasons to gain perspective of consistency of yield and quality when grown in different environments.

It should be noted that the two cultigens from BASF/Nunhems, Nun 22102 and Nun 22104, yielded high quality seeded fruits which might be a good option to use as a pollenizer if the grower has a market for seeded watermelons.