I did the harvest today, and here are the results, in terms of grams of potato per plant:
| Yukon Gold | 144 |
| Dark Red Norland | 113 |
| Kennebec | 283 |
| Red Gold | 244 |
| Kattahdin | 75 |
| La Ratte | 13 |
| Papa Cacho | 27 |
This is pretty awful. For comparison, just planting random store-bought yellow potatoes gives around 250 g/plant, while better-performing varieties (Island Sunshine and Yukon Gem) on my farm have produced 400-800 g on average or even well over 1 kg in lucky cases.
The one promising bit here is the Kennebec:
Kennebec did the best in this trial, basically due to surviving a few days longer before dying back. I might try this variety again, starting from fresh imported seed potato, on newer garden beds.
All the other varieties died back before producing any substantial potatoes. As I’m not a botanist with a laboratory, I have no way to determine what causes the die-back – presumably some fungal blight, but which one? From looking at online images, I would say that the die-back looks somewhat like late blight, but not really at all like early blight. There are also dozens of other potential fungal and viral potato issues, and no way to know which I’m encountering, which is frustrating.