Ken Allan 
Vegetable
Garden
USDA Georgia Jet versus Canadian Georgia Jet
I got my original stock of Georgia Jet from a US mail order garden seed supplier who listed it simply as 'Jet'. After some research I concluded this must actually be ‘Georgia Jet’. A few years later, I visited a Canadian government variety trial and was able to take cuttings of their Georgia Jets; I grew them alongside my own and found them to be identical.
Georgia Jet has been the most consistent variety in my garden and performs, in comparison with other varieties, in much the same relation as Georgia Jet performed for Roger Kline in his trials at Cornell in northern New York state.
During the time I was writing my book I got reports from US gardeners who had tried Georgia Jet and found it did no better for them than their favourite variety. Roger Kline had found, over a period of 10 years, that Georgia Jet outyielded all others in most years. Nevertheless, other varieties occasionally pushed Georgia Jet into second place (though never the same variety twice), so I was not surprised, at first, when I got reports of another variety having a better year than Georgia Jet. Still, I got enough of these reports to make me wonder.
When I had an opportunity to obtain the ‘official’ Georgia Jet from the USDA, I did so. In the summer of 1999, I grew rows of USDA Georgia Jet and my Georgia Jet, side by side, to compare appearance and yield. The differences were much greater than expected. The leaf, for starters, was different. Both have a maple leaf sort of shape and some of the leaves on my Georgia Jet were identical to leaves on USDA Georgia Jet, but in general the leaf of USDA Georgia Jet was more deeply serrated and had more points. The vines of USDA Georgia Jet were shorter than my Georgia Jet. The vines of USDA Georgia Jet had a tendency, when sending out a new branch, to grow vertically (I have observed this in one other variety) before bending over to become a vine.
When I dug the fleshy roots, my Georgia Jet had smoother skin which was more uniform and a brighter pink-red colour. The yield of my Georgia Jet was somewhat better. Any tuber less than 2" diameter and 6" long becomes a seed root. From USDA Georgia Jet the average yield per plant was 1.3 lb seed roots and 1.6 lb bakers. From my Georgia Jet the average yield per plant was 1.3 lb seed roots and 2.7 lb bakers. This larger proportion of large tubers is especially important to northern growers since the larger tubers are the most useful (and in a poor summer, my Georgia Jet still produces some useful tubers while other varieties produce little more than seed stock). The two Georgia Jets have similar flavor but USDA Georgia Jet is a little richer in flavour, brighter in orange colour and has a drier mouth feel. USDA Georgia Jet is more prone to cracking.
So what has happened? There are two possibilities.
One is that I didn’t have Georgia Jet in the first place. I think this unlikely but it isn’t impossible. Plant breeders evaluate breeding lines which never get released as named varieties. If one of these breeding lines got into general circulation it could have been given an unofficial name and ended up on a seed seller’s list.
More likely is that the original Georgia Jet seed stock got contaminated by mutations before it was passed on to the USDA. Mutations are quite common in sweet potatoes and the guardian of the seedline must be vigilant to remove atypical plants. However, Georgia had disease problems, especially with Georgia Jet, and when a plant is diseased, mutations are much more difficult to spot.
What this means for growers in the northern USA is that you cannot assume Georgia Jet is best for you. Because of border restrictions I can’t ship my Georgia Jet to you; and USDA Georgia Jet has given "Georgia Jet" such a poor reputation among plant professionals (because of the cracking, disease, and poor yields) that it will not be easy to get them to import my stock of Georgia Jet and clean it up (ensure it free of disease) for your use. You will have to evaluate the varieties you can get and go from there.