Leading up to 2012, we had tried lots of different eggplants for yield and flavor, finally settling on Nadia as our favorite. The summer of 2012 was hot, and we discovered 'Nadia' eggplant has trouble setting fruit in hot weather. How hot are we talking about? We're in central Virginia, winter plant hardiness Zone 7a, and AHS heat Zone 7.
You can access state heat zone maps and a key to the zones here. There are 12 zones on the map, indicating the average number of days each year that each region has "heat days" – those with temperatures over 86 degrees Fahrenheit (30C). That is the temperature at which plants start to suffer physiological damage from the heat.
Heat Zone 1 has only 1 day each year above 86 degrees F. Zone 5 has 30 to 45 days, Zone 6 has 45 to 60 days, Zone 7 has 60-90 days above 86 degrees F. Well, quite a few were a deal hotter than 86F. Personally, I find a big difference between days over 90F and those over 95F.
We were disappointed to have to go back to the drawing board to find a variety with better heat tolerance. With climate change rolling in, we decided it really would be wise to prepare for more hot summers and trial some heat-tolerant eggplant varieties. We ruled out unusual shapes and colors, because what we have a demand for is the classic "teardrop oval" eggplant shape in classic purple-black.
2016 is our fourth year of trials and the first summer that actually had some very hot days. We have joked that we can keep hot summers at bay by doing heat-tolerance eggplant trials! You can read our year-by-year accounts on my blog, Sustainable Market Farming.
In 2013, we compared 'Nadia' with 'Epic', 'Traviata', and the open-pollinated 'Florida Highbush'. We counted fruit harvested from each variety but didn’t weigh them.
'Traviata' yielded well, with an average of 7.3 fruits per plant, 'Florida Highbush' 6.3, 'Nadia' 6.1 and 'Epic' only 4.4.
We’d planted the 'Epic' at the dry, stony end of the bed and wondered if that had affected yields. As we found out in 2014, it certainly had! We thought that 'Florida Highbush' had smaller fruit, but we weren’t sure, as we hadn't weighed them. We decided to do that the next year.
In 2014, we grew the same four varieties and this time recorded the weight of each harvest as well as the number of fruit of each variety. That year we got better results all round: 'Nadia' gave 13.4 fruits per plant, 'Epic' 12.5, 'Traviata' 11.7 and 'Florida Highbush' lagged behind with 6.8 fruits per plant.
We forgot to write down which variety was at the dry, stony end that year! We discovered that the size and weight of each fruit was very similar for all four varieties, varying only from 'Epic’s' average of 0.61 lbs per fruit to 'Traviata’s' 0.64 lbs per fruit. In case you're curious, we got a total of 927 eggplants, weighing in at 582 lbs – an average of 0.63 lbs each.
In 2015 we tested the same four varieties again, along with another reputedly heat-tolerant open-pollinated variety, 'Florida Market', which turned out to have visibly smaller and rounder fruits.
'Florida Market' had a lower yield. Unscientifically, it was at the unfairly dry and stony end, but it did so poorly compared to the others, that we scratched it from future trials.
In 2015, 'Epic' did best, both in number of fruit/plant (10.7) and weight/fruit (0.77 lbs). Good thing we didn’t give up on it after growing it in the gravel in 2013!
'Traviata' produced 8.9 fruits/plant, 'Florida Highbush' 8.2, Nadia only 8.0 (we got a high rate of culls too), and 'Florida Market' only 7.5 (small fruits at that). We got a total of 812 eggplants in 2015, weighing 564 lbs, a slightly higher weight average than 2014, at 0.7 lbs. Our eggplant harvest peaked on August 19.
For 2016, we decided to grow only 'Nadia', 'Traviata' and 'Epic', and to plant the same number of each, to make our lives simpler. Our first eggplant harvest was 7/18. At the end of July, the 26 'Nadia' plants had produced 31 eggplants, the 26 'Traviata' 30, and the 26 'Epic' yielded most at 73!
The 'Epic' were largest too, at 0.9 lbs/fruit ('Nadia' 0.8, 'Traviata' 0.7 lbs). The numbers include commercial culls, which we kindly call "Use First" and take to our kitchen. The cull rate of 'Traviata' was the highest.
Continuing through August, which has had some very hot days, 'Nadia' has produced 125 eggplants, averaging 0.76 pounds each; 'Traviata' 124 averaging 0.72 pounds; and 'Epic' a staggering 287, averaging 0.9 pounds each. The cull rate for 'Epic' was 22%, for 'Traviata' 29%, and for 'Nadia' 21%.
'Traviata' had one particularly bad day for culls. At the end of the season I'll try to correlate the full season's results with the weather data. Check back in November, here or at Sustainable Market Farming.
Photos by Nina Gentle (Epic and Traviata) and Kathryn Simmons (Nadia).”
Pam Dawling manages the vegetable gardens at Twin Oaks Community in central Virginia. She often presents workshops at MOTHER EARTH NEWS Fairs. Pam also writes for Growing for Market magazine. Her book, Sustainable Market Farming: Intensive Vegetable Production on a Few Acres, is available in the MOTHER EARTH NEWS Store and at Sustainable Market Farming. Pam's blog is on her website and also on Facebook, and you can read all of her MOTHER EARTH NEWS posts here.
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