Sunday, 29 May 2016

Sweet potatoes and some sweet sweet potato seed

Slips ready to be potted
Summer's here! Well, that's what it feels like at least. We've been having an unusually warm May here, with a monthly average some 3°C higher than usual and extended periods of hot and sunny weather. As a result, the garden has gone into turbo-mode and I've already managed to plant most of the sweet potatoes. Usually the beginning of June is a more reasonable time for this, though I never seem to have the patience to wait that long. Now though, some are already starting to put out new growth, so my impatience is actually paying off for once. I have a bunch of latecomers that are refusing to put out slips, but with tropical weather forecasted for the coming week, they'll catch up soon I hope. Barring some serious force majeur, that means I now have a final list of the varieties I'll be growing this year:
  1. T65 - reliable producer, does not flower.
  2. Georgia Jet - should be a reliable producer, but did badly for me last year. I obtained what I hope is a better strain, so let's see. Should flower easily.
  3. Purple - (I called this Nordic Purple before, but I'm pretty sure it's the same variety that is elsewhere known by the name Purple) - purple-fleshed variety, not very productive but flowers profusely.
  4. Bonita - only had one plant of this last year, so it's hard to say how productive it was, but it flowers.
  5. Burgundy - same as with Bonita, plus the tiny tuber I managed to overwinter is just starting to put out slips. Flowers.
  6. 'Nordic White' - unknown white-fleshed variety, fairly productive here, and flowers.
  7. 'Nordic Orange' - medium productive, but I'm not sure if it flowers. I thought I saw some flowers on it two years ago. If it doesn't flower this year, I'll drop it.
  8. Mystery - a Georgia Jet mutant, haven't grown this before, but if it's anything like Georgia Jet it should flower easily.
  9. ? - a complete mystery this one! 
  10. Bunduguza - starchy white-fleshed African variety, lowish yield, no flowers.
  11. Burundi - starchy yellow-fleshed African variety, lowish yield, no flowers. This was the best out of all the African varieties I tested last year.
Then there's two varieties from the highlands of Papua New Guinea, a region that apparently can get quite chilly at night (relatively speaking of course, it's still a tropical area), and so should theoretically be somewhat cold-adapted. There's some hope, therefore, that compared to your average I. batatas variety, these two will feel a bit more at home here in maritime Malmö. They will join the others in the garden, provided they put out some slips soon. Both have roots, and one has a tiny slip forming, but I sure wished they'd hurry up a bit:
  1. Kainantu 
  2. Aiyura
I. batatas seed sprouting
And then, just as I thought I would get away with growing just 11+2? varieties this year, I received a small package with seeds. That is, proper sweet potato seeds, that rarest of things! These too are from the Papua New Guinean highlands. In practice, I suppose the chances are fairly slim that anything useful will come out of them. I generally put more faith in efforts to produce seeds under northern growing conditions, as Telsing Andrews has succesfully done last year, and as I hope to achieve myself this year. Nevertheless, a tiny chance is still a chance worth pursuing, plus it will be loads of fun to play around with these seeds. I promptly scarified some of the seeds with sandpaper, soaked them for half a day, and sprouted them. Germination rate was higher than I had anticipated, of the 35 seeds I soaked, 29 sprouted. That's 29 new sweet potato varieties, right there. Quite a bit of difference showed up in the phenotypes, with some seedlings showing intense red leaf colouring, some being completely green, and some lying somewhere inbetween. True leafs are deltoid or cordate, with a few of the seedlings having toothed edges.
About half of the seedlings
The batata battle plan for 2016 then: 1) Grow everything under a floating row cover for as long as practically possible, in order to speed up flowering. I've given this some thought and I didn't want to go the plastic mulching route just yet, I'd prefer to get seeds without too much 'cheating' technologies. Call me a botanical luddite! 2) Evaluate varieties for flowering onset, potential seed-set, and yield. 3) Share flowering varieties with collaborators in order to increase the chances of seedset under nordish conditions. 4) Acquire more flowering varieties. 5) Repeat.

 As simple as that!


  1. Excellent work. Maybe 2016 will be the year you produce your own true sweet potato seeds. Good luck!

  2. Yes, nice progress! Great germination on those "wild" type seeds, and maybe a fair bit of diversity there too.