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I've just ordered 1kg of heirloom seed potatoes but I only intend to plant 500g or so.

Going forward, I intend to harvest true seed from their fruits, but I'd like to keep a backup in case blight strikes in year 0.

How long can I viably store the seed potatoes and what would be the best conditions?

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    Would you have the resources for tissue culture? That is how seed banks maintain heirloom potatoes. Otherwise you'd want to plant and harvest each year – J. Musser Jan 24 '17 at 2:39
  • Do you mean they have a team of unpaid interns continuously nursing the cultures or do they just freeze the petri dishes and then culture them back to life? – user10810 Jan 24 '17 at 3:11
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    Here's the example I was thinking of: blog.seedsavers.org/blog/seedpotatoes – J. Musser Jan 24 '17 at 4:06
  • @J.Musser , I believe the tissue culture described in your link is similar to the one applied to grapevines in order to produce virus-free strains from infected plants and to refresh the source plants from virus-free stock. There is no description of the tissue-storage process unless they aren't storing the tissue at all and indeed keeping plants alive through the whole process, which is not what I'm asking. – user10810 Jan 24 '17 at 4:53
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    I think they are growing plants as well as maintaining tube cultures. I commented rather than answering because although I know how long seed potatoes store, I'd want to research on alternate methods such as this one for maintaining varietal purity and vigor. – J. Musser Jan 24 '17 at 4:56
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Seed potatoes by the time you get them from your supplier have a chronological age and a physiological age. Depending on how well it has been kept by the supplier, its physiological age may be older then its chronological age would suggest. Factors that increase physiological age include crop stress ( high temperatures, low moisture, frost damage, disease ), damage from handling, and high storage temperature. A seed potato that has been purchased still dormant will last longer.

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One of the best-known potatoes for storage is Russet Burbank because it has a long dormancy period. The longest period observed for this potato variety over an observation period from 1999-2013 is 200 days at 42 deg F. Storing potatoes at lower temperatures causes sugar formation which is generally undesirable when used for consumption. Herbicides are misted onto potatoes for sale as produce to inhibit sprouting, and commonly chlorpropham is used. This may well affect the viability of seed potatoes, and there are alternatives such as ethylene and essential oils which can inhibit sprouting for a few weeks without affecting viability.

However, the problem is that unlike a seed which is largely metabolically inactive, a seed potato is actively respiring and physiologically ageing. This will eventually trigger the physiological processes that cause sprouting, and measures to try and stop this may well affect the viability for its use as seed. Since you've already ordered tubers as seed, the approximate maximum duration you can keep them as seed before they break dormancy is 200 days but will depend on what variety you ordered and you might be able to extend that for a few weeks without affecting viability using seed inhibitors.

BTW, if you're interested in developing or keeping potato varieties, you can check out the Kenosha Potato Group on facebook, with over 2000 members, and the Seed Savers Project

Edit: I purchased .6 mm mesh last year to protect against the potato tomato psyllid, and it's also has been found to protect against potato blight (Phytophthora infestans) in one part of this country. So, you could consider using this to see if it protects your crop.

http://www.vicspa.org.au/f.ashx/The-young-the-old-and-sproutless_-seed-age.pdf

http://www.potatogrower.com/2013/09/understanding-dormancy

https://www.nappo.org/files/9714/3753/7437/Potato_sprout_inhibition_ST_e.pdf

  • Interesting information but the answer lacks a conclusion. Store them in the refrigerator with some ripe fruit and hope they aren't past the little tuber stage by the time you plant them? If dormant, Spring seed potatoes would at least make it to a Fall planting, right? – user10810 Jan 24 '17 at 8:39
  • @jbcreix longest you can hope is 200 days without treatment, and maybe a few more weeks using sprout inhibitors. But that's not going to make a year but you're not going to be able to alter the genetic programming for whatever type of seed potato you've already got. – Graham Chiu Jan 24 '17 at 8:45
  • I'm curious about the length of the non-dormant stages and the viability of the small-tuber stage, in particular. I know that Yams that sprout off season put part of their stored reserves into a new tuber producing two smaller viable tubers. I wonder how "gone" the small tubers are in potatoes. Weak plants unfit for production beats no plants. – user10810 Jan 25 '17 at 4:45
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The place to "store" your seed potato to have viable seed potatoes next year is in the ground, with roots coming out one direction and plants going the other.

As for getting blighted, your options are to grow in multiple separated locations and hope they don't all get blighted, or order new seed. One blight-prevention option might be to grow in a polytunnel and use drip irrigation, so the foliage never gets wet.

As for the seed from fruits, it's wonderful that you want to become a potato breeder, but as far as I am aware, you will not get the same variety of potato if you do happen to get seed - you might develop an interesting new variety, or you might not, but you won't get the same one you started with.

Edit, add: In your comment above you state:

indeed keeping plants alive through the whole process, which is not what I'm asking.

...which means that you don't understand what a "seed potato" is. If you don't keep it alive, you have compost material, not a seed potato.

  • By alive I meant not dormant and frozen solid like the seeds in storage for other plants that are good for centuries as long as the freezer stays on. I think it should be possible to preserve a few potato germ cells given that we routinely freeze human embryos. I understand that it likely won't work for whole potatoes any more than it does for whole humans. I'll try all methods including planting in a rain-free spot and see what works best. – user10810 Jan 25 '17 at 4:32
  • IIRC, blight doesn't need water, just high humidity in order to infect potato plants. – user10810 Jan 25 '17 at 4:32
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    "The actual infective spores are released from the sporangia into water and need to swim in a water film before settling on the plant surface and penetrating into leaf tissues; " according to rhs.org.uk/advice/profile?PID=217 – Ecnerwal Jan 25 '17 at 4:49
  • Shoot, which blight exactly are you talking about? The ones I know that also infect tomatoes, eggplant and peppers infect via water not humidity. The spores are in the soil, water picks them up and splashes on the vegetative above ground growth. Then the entire plant is instantly infected. Heck, Ecnerwal has this already addressed!! – stormy Jan 25 '17 at 19:59
  • @Ecnerwal In zone 5 maritime influence I was able to harvest potatoes all winter long from my raised beds. But any lower zone forget it. They froze and turned to mush. I am now storing my harvest between lots of sheets of newspaper in slightly cracked insulated 'coolers' in a slightly heated shed. Your answer is excellent, Ecnerwal. I love getting my seed potatoes every year to include my favs (German Butterball) and trying something new. If I had ONE plant to grow in my vegey garden it would be potatoes...certified by someone else!! – stormy Jan 25 '17 at 20:06

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