Saturday, 26 November 2016

Seed!, Seed!, Seed!, Or: A bright beginning to batata breeding (for beginners)

So. Things have been a bit mad around here for the last few months, what with defending a dissertation and all, which means a lot of things became hopelessly delayed, including harvesting things, and writing blog updates about harvesting things. I'm slowly getting there though, even though I will abstain from making promises of more regular future updates. It is what it is, my tiny cohort of somewhat-loyal followers!

The sweet potato plot in late August - with bagged pods
First up, this year's great I. batatas success. Damnit.. now I already gave it away. To recap, I had 13 different sweet potato varieties at the start of this growing season. Burgundy never made it out of the house, so only 12 of them ended up happily populating the batata plot, together with some 20 seedlings derived from seed originating in the Papua New Guinean highlands (don't ask...). Of these 12, the two Papuan tubers I had (unsurprisingly) proved somewhat too exotic for these latitudes (the fact that they were late to produce slips probably didn't help) and didn't yield any offspring that I could keep for next year. This left me with 10 varieties that all considering did rather well I think. The table below gives the yields, and my rough attempt to evaluate how much space I allocated to each variety, in order to give an estimate of the relative yields. I should underline that the space allocations are estimates that probably have a significant error margin, since, well, I completely failed to measure them properly prior to harvesting. Still, it should give a general idea of what varieties did best this year. At least the general direction of these numbers corresponds to my (very unbiased, naturally) subjective impressions of the harvest.

Sweet potato harvest table - 2016

As you can see, the most productive variety in my garden this year was not T65 (surprisingly, given its reputation as one of the most cool climate-tolerant, and given its indisputed domination in previous years), but Nordic White, followed by an unnamed variety originating from Telsing (and that might, in fact, be T65 - you didn't think this was going to be easy or straightforward, did you?). Georgia Jet and its clone, Mystery - those sweet potato superstars of the temperate Americas - again failed to live up to its promises here in Sweden. I suspect that even though GJ is a short-season variety, it requires fairly high temperatures to produce decent-sized tubers, and we certainly have cooler summers here than in much of the northern US and southern Canada. That being said, this was in many ways a dream year (in relative Swedish terms) for sweet potatoes here, with a very warm spring followed by a fairly decent summer, followed again by an unseasonally warm September. I've added a temperature analysis below: overall this growing season was about 1.2°C warmer than the same period in 2015. As for a bit more details on my cultivation practices, all of the listed varieties were grown outside, on ridges, without ground cover. Plants were covered with row covers for the first half of the season, until around the end of July, when the first flower buds appeared.

This is most of the harvest except for Bonita, Nordic White and Nordic Purple

As expected, the PNG seedlings didn't produce all that much. Nevertheless, it was an interesting little experiment. There was large variety in terms of growth habbit, leaf shape and colour, tuber morphology and skin and flesh colour among the seedlings. White, cream, purple-ish and various shades of copper-coloured roots were all present. One plant yielded three medium-sized white tubers, which I will attempt to keep for next year. The rest will be discarded. All of this gives me little reason for sorrow because, my friends, I now also have more promising seeds to play with! The (F) behind Georgia Jet, Bonita, Nordic White and (Nordic) Purple indicates that these varieties flowered and set seed this year, which, as the internet might have told you, is somewhat of an anomaly in batataland. Georgia Jet produced only one pod (I believe), but might have contributed pollen to the others. Bonita and Nordic White were earliest  to flower and put out quite a lot of pods in the end, though the absolute flowering and seed-producing champion was Purple, which flowered some two weeks later but when it did made the others pale in comparison. I should note that Bonita and Nordic White, which I obtained from different sources, appear very similar and I'm not entirely sure anymore that they are in fact distinct varieties. For the time being, however, I will treat them as such. None of the seeds fully matured on the plants before I needed to harvest the tubers in the first week of October, so I cut off all of the stems with pods on them and put them in water indoors, until they had fully dried. I've tallied up the totals last week, and in total I now have 104 sweet potato seeds to play with next season. Excuse me while I make a little victory dance. I also got my hands on seed from three other varieties, produced by a fellow batata enthusiast in the US, so there should be a bit of diversity here to start working from. Now it's just a matter of upscaling seed production and growing out tens of thousands of seedlings in order to start selecting for adaptation to northern Europe. Easy! Maybe someone wants to contribute with some land and some long-term research funding?

Sweet potato seed pod
Malmö weather - 2016
2016 compared to 2015: avg temp between June and October 2016 was about 1.2°C higher than 2015


  1. I love all the graphs and details you add on here. Thank you.

  2. I might be able to contribute with some land. We live in Flyinge 10 minutes north of Lund.