We’ve always grown potatoes occasionally, since I was growing up here, but recently I became more interested in really knowing potatoes and hopefully increasing production. To this end, I started a spreadsheet to track planting and harvests, and ordered some seed potatoes for variety trials.
Background: We used to just use organic potatoes from the health food store. Some would start to sprout before we got around to eating them, and they got planted in the garden. The yield was never very good, but at least it made a few small potatoes per plant, so it was worthwhile. We had no idea what we were doing, but it was OK.
In 2019, I ordered sample packs from Wood Prarie Family Farm (“Certified Organic Maine Certified Seed Potatoes”). It included four varieties – Fingerling, All blue, Caribe, Yukon. The yield was (what I now know is) dismal: under 300 g/plant, except for one set of All Blue which almost managed 600 g/plant.
I continued to plant our rotating set of unknown varieties as well (saved over the years from those store potatoes). These “misc yellow” and “misc red” varieties also produced poorly, the yellows never exceeded 300 g/plant and the reds were lucky to reach 300-600 g/plant.
I eventually did a lot of reading on potatoes online, and a textbook on potatoes from the library. I learned a lot about potato history, genetics, and diseases. I learned that by re-planting our own potatoes year after year, we were probably accumulating an increasing number of potato diseases. The only way around that is to order seed potatoes from a very cold place (like Maine) where the winter kills most pathogens.
From observation, the overwhelming factor that determines yield, in our gardens, is how long the plants live before dying back (from unknown blights or diseases). Nearly everything we plant dies back prematurely, when the potatoes are still small, and that completely explains the low yields. It doesn’t appear to be insects, or rot, or anything visible. Just plants dying back too soon.
So, in 2020 we ordered a more serious amount of Maine potatoes. We are at 2500′ in Ahualoa, 80-200 inches of rain/year, so we knew we need something that tolerated wet conditions. We chose these cultivars, which Wood Prarie described like this:
- Red Norland. Yield medium-heavy, Late Blight Tolerance Medium.
- Yukon Gem. Yield medium-heavy, Late Blight Tolerance Medium-high.
- Island Sunshine. Yield medium, Late Blight Tolerance Very High.
As the spreadsheet shows, the yield has corresponded loosely with the “blight tolerance”. Red Norlands did the worst (264 g/plant), Yukon Gem significantly better (692 g/plant). The Island Sunshine did something fascinating! I planted a long 21-foot bed of 30 plants. Most of the bed died back early, and averaged a poor 350 g/plant. But 4 plants – all next to each other, in the middle of the bed – somehow escaped the dieback. They continued to grow huge, and produced an astonishing 1294 g/plant.
My theory, at this point, is that our garden soils, from years of growing a large variety of random vegetables including potatoes, have accumulated a load of potato pathogens, and that somehow those four plants (in a relatively newly expanded area of the garden) got lucky and grew in a patch of soil that had none of the (fungal? blight?) pathogen.
I’d love to believe that it might be genetic, that those 4 Island Sunshine plants might have some genetic variation that caused them to overcome whatever issue our soil has. But, what I’ve read about potato genetics says that’s highly unlikely. Of course, I’ll be re-planting just the potatoes from those four plants, but chances are, they will be limited by the soil I plant them in, not their genes.
Today, UH-CTAHR did a small distribution of seed potatoes for citizen science experimentation. I am delighted they are doing this. I picked up my seed potatoes today. These are the varieties I got, along with what I could find on their supposed disease resistance:
- Yukon Gold – “medium tolerance of late blight”
- Papa Cacho -“robust plants with obvious resistance to late blight”
- Red Gold – “resistant to potato leafroll virus and potato virus Y and moderately resistant to common scab, but is susceptible to potato virus a and potato virus s.”
- La Ratte – “resistant to scab and viruses”, “low yield”
- Dark Red Norland – “resistant to scab, growth cracks, hollow heart, early blight, and rhizoctonia (black scurf)”, “medium tolerance of late blight”
- Katahdin – “consistent performance”, “moderate resistance to scab”
- Kennebec – “good field resistance to late blight”
Of these, I’ve already grown the Yukon Gold and Red Norland, and seen very low yields. The Kennebec and Red Gold might do OK? It’s hard to guess; we’ll find out. The problem with doing a trial like this, though, is that there are only 3 spuds in my Kennebec bag, with cutting, enough for probably 5-6 plants. What if those few plants get lucky or unlucky with a particular part of a garden bed, like the Island Sunshines seemed to? In that case, any variety-specific traits are overwhelmed by the variation in the soil issues, and we won’t know if the variety is good or not.
