Arkansas Fruit, Vegetable and Nut Update

Year 1 Results: Blueberry Variety Trial in Clarksville, Arkansas

by Keilah Barney, Dawn Braxton and Amanda McWhirt - November 22, 2024

3 rows of blueberries planted on a farm

A blueberry variety trial was initiated in 2021 at the University of Arkansas’ Fruit Research Station (FRS) in Clarksville, Arkansas marking the summer of 2024 as its first harvest season. This trial consists of 20 varieties across 3 plant types, Northern Highbush, Southern Highbush, and Rabbiteye. See Table 1 for the full list of varieties included in the trial. All varieties are being evaluated for their yield potential, fruit quality, and fruit taste.

The trial location in Clarksville sits right on the line between hardiness zones 7b and 8a. The low temperature for the 2024 harvest season reached 0° F in January. Sulfur was applied in early spring to amend soil pH. Fertilizer applications consisted of Ammonia Sulfate ((NH4)₂SO₄) applied 3 times throughout the growing season.

Table 1. 2024 Blueberry Variety Trial: bush types, varieties, and their harvest dates.

Yield and Berry Size

Harvest containers with different varieties of blueberries.

For their first harvest season, these varieties displayed noticeable differences between the average yield per plant. Harvests occurred once a week beginning May 21^st and ending August 2^nd, 2024.

The two varieties that had the highest yield were Alapaha and Vernon at around 10 lbs. of marketable fruit per plant (Figure 1), both of these cultivars are Rabbiteye types. A freeze in mid-March caused significant damage to the flowers of some of the earlier blooming varieties, particularly the Southern Highbush and Northern Highbush types. This damage contributed to severely reduced yields, in some cases to less than 1 lb. per plant.

Varieties seemingly most affected by the late freeze were Bluecrop, Blueray, Duke, New Hanover, Summit, and O’Neal. While the blooms on the Northern Highbush varieties were not as developed as the blooms on the Southern Highbush and thus could tolerate colder temperatures, there was still some damage noted. Another contributor to decreased yield in the Northern Highbush types could be their smaller plant size. These varieties had less vegetative growth compared to the Southern Highbush and Rabbiteye types possibly due to Arkansas’ high heat, so they may perform better in locations further north.

Figure 1. Marketable yield (season long totals) per plant of twenty blueberry cultivars at Clarksville, AR in 2024.

Figure 2. Berry size (g) of twenty blueberry cultivars in Clarksville, AR in 2024.

Fruit Quality, Flavor, and Appearance

A blueberry plant with ripe berries being harvested into bucket.

Samples of each variety were collected at three points during the season to determine fruit brix, pH, and citric acid content. These are important in determining fruit flavor and sweetness. Brix is a common way to measure the sugar content in a liquid, in this case, blueberry juice. Brix content ranged from 8 – 13.2°Bx, Bluecrop had the lowest fruit Brix, and Ochlockonee had the highest. Fruit pH ranged from 2.8 – 3.3, Top Shelf and O’Neal respectively. Titratable acidity (Citric acid) ranged from 0.27 – 0.85%, Ochlockonee and Blueray respectively (Table 2).

A similar variety trial on Rabbiteye blueberries that was conducted in Alabama by Auburn University saw much higher brix numbers than we did on the Rabbiteye types here in Arkansas (Coneva, et al. 2023). Of the Rabbiteye varieties used in our trial, ‘Overtime’ and ‘Brightwell’ were the only ones not included in Auburn’s variety trial. From the nine varieties they evaluated, the average brix content ranged from 14.6 – 16.9 °Bx, Climax the highest and Ochlockonee the lowest.

Table 2. Average blueberry fruit brix, pH and titratable acidity (citric acid %) for twenty cultivars in Clarksville, AR in 2024 sampled at three time periods.

Two taste tests were conducted during the harvest season. These tastes tests were led by Dawn Braxton (UARK Horticulture Undergraduate student and summer intern). The taste test panel consisted of faculty, staff, and visitors present at FRS on the day of the taste test. There were 27 respondents for the first taste test and 15 for the second bringing the total responses received to 42. The pool of respondents consisted of both men and women ages 20 and up. When participants were asked how often they ate blueberries 5% ate blueberries daily, 26% weekly, 29% monthly, and 41% only a few times a year.

Participants were asked to rank the fruit on a scale of 1 – 5, 1 being the worst and 5 being the best for each category. Fruit was judged based on berry color, shape, size, overall appearance, texture, sweetness, sourness or bitterness, overall “blueberry” flavor, and the participant’s overall impression for each variety.

Because of the variation in harvest dates across varieties and some varieties yielding so little, only 13 of the varieties made it into the taste test. Of the varieties that were included, the variety that received the best overall “blueberry” flavor was Blue Ribbon, followed by Legacy and Bluecrop. Blue Ribbon, Top Shelf, Legacy, and Climax lead the pack in terms of overall appearance. While Krewer ranked highly for size due to its large berry, it fell short likely due to its pale blue color and undesirable “belly button” like appearance as described by a few of the taste test participants.

Despite some concerns of gritty texture in Rabbiteye types, in our taste tests they performed similarly to Northern Highbush and Southern Highbush types. For the highest rating of best “overall impression”, the winner was Blue Ribbon, followed closely yet again by Legacy, and Bluecrop (Table 3).

Table 3. 2024 Blueberry variety trial: average flavor and appearance ranking as determined by taste test panel.

Figure 3. Average overall impression from 2024 blueberry taste test panel.

Conclusion

Alapaha and Vernon had the highest total marketable yield at 10.3 and 10.1 lbs. per plant with average berry sizes 1.21 and 1.58 g respectively. How they hold up against the other varieties for flavor is yet to be determined as these varieties did not make it into the taste test this year.

Blueberry variety "Blue Ribbon" in the field.

Blue Ribbon and Legacy performed well in the taste test for overall appearance, overall blueberry flavor, and overall impression. Though well received in the taste test, their yields were moderate at only 5 lbs. per plant, but keep in mind these plants are still relatively young. This lower yield in 2024 could be a result of spring frost damage to blooms, but further data collection will be needed to get a better scope of their yield potential.

As a reminder, this is only one year of data collection. Further study and observation could present different results as the plants continue to mature and we see how they perform over several years.

References

Colena, E., et al. 2023. Early performance of newly released blueberry cultivars with improved fruit quality characteristics (blog post). https://smallfruits.org/2023/01/newly-released-blueberry-cultivars/. [accessed 8 Nov 2024].