Potatoes: Extracting true potato seed

As promised, here is the procedure that we use to extract potato seeds.  There is no new information here; this is basically the same method recommended by Tom Wagner at his TaterMater forums, but condensed into step-by-step form.  (If you are wondering why you should save your own potato seed, start here.)

Rinsed berries, ready for extraction

This is not the only way to extract potato seeds.  The fermentation method is less work (in fact, you can let nature do most of the work) but the results may not be as good.  The fermentation method also takes more time and involves having a lot of containers of fermenting liquid sitting around if you have lots of berries to extract.

You can find other methods by searching for tomato seed extraction methods, which will also work for potato seeds.

We even have a neighbor who occasionally just plants a potato berry in the ground and that seems to work for him.

Requirements:

  • 1 blender
  • 1 strainer through which potato seeds can pass
  • 1 strainer through which potato seeds cannot pass
  • 2 tbsp plain chlorine bleach
  • 2 tbsp dry TSP (trisodium phosphate, usually available at hardware stores)
  • 2 bowls with at least a three cup capacity
  • Paper to use as blotter
  • Some potato berries

Steps: 

1. Wait until your potato berries have softened up some.

They don’t have to be mushy, but should yield to moderate pressure.

2. Rinse the berries.

Might as well get any dirt off before you start.  This may also help to cut down on transmission of some diseases. 

3. Dump the berries in the blender.  

Don’t fill more than half way or you’re asking for a mess.

4. Cover the berries with water by about an inch.

Again, make sure to leave some space in the blender pitcher because this is going to foam up quite a bit. 

5. Blend until the berries are reduced to pulp.

It shouldn’t take more than 30 seconds.

Once you are done blending, add water to fill the blender pitcher.  This will help break up the pulp.

6. Let the seeds settle out of the pulp.

There are a few ways to go about this.  You can simply wait, perhaps even overnight, for them to separate on their own.  You can stir the pulp, which speeds up the process considerably, but could still take a while.  Or, you might notice that we have the blender set up on top of a washing machine.  A washing machine on spin cycle acts as a shaking table, so you can just leave the blender there through a wash and that will help along the separation.

7. Pour or float off the pulp.

If you are careful and slow, you can just pour it off.  But, if you stir up the seeds, you may end up pouring some of them down the drain.

The easiest way to do this without stirring up the seeds is to put the blender pitcher into the sink and run water into it slowly.  As the water rises, it will carry off the pulp and you’ll be left with mostly seeds.

Before pouring off debris

After pouring off debris

8. Strain the pulp from the seeds using a strainer that the seeds can just fit through.

The goal here is to remove the last bits of pulp and get down to mostly seeds.

Put the strainer over a large bowl and just keep running water through it until all the seeds have passed through.

Seeds fall through this standard kitchen strainer

Debris gets caught

9. Pour off the water and seeds through your fine-meshed strainer.

This time, you want the seeds to stay in the strainer. 

It is OK if there are still tiny bits of pulp and dirt.  You would have to work really hard to get rid of the really small stuff.  It will dry out with the seeds.

Seeds are caught by this fine mesh strainer

10. Rinse the seeds under warm water to remove gel.

There is a lot of gel coating those seeds and this step can take a while – five or ten minutes if you are processing a large batch.  Just keep testing until the run off isn’t slimy.

11. Make TSP solution.

Put two cups of water in a bowl and add 2tbsp of powdered TSP.

Stir it until it is fully or mostly dissolved.  Warm water will dissolve the TSP more easily.  TSP is fairly harsh; try to avoid getting it on your skin and rinse it off if you do.

(You want about a 10% TSP solution.  TSP is about 24 grams per tablespoon and there are about 240 milliliters per cup.  Percent solutions are generally worked out as mass solute / volume solvent *100, so this works out very conveniently as a nearly 10% solution.)

12. Soak the seeds in the TSP solution for 20 minutes. 

The TSP is a detergent and will help to break down the remaining gel that surrounds the seeds.  The gel is a germination inhibitor, so the TSP soak should help to ensure good germination.

Without the TSP, you might need to do additional soaking of the seeds before you start them to help them overcome the inhibitors.

13. Rinse the seeds under warm water.

Just a quick rinse this time.  You just need to get the TSP off of the seeds.

 

14. Make bleach solution.

Put two cups of water in a bowl and add 2tbsp of plain chlorine bleach.

This will make a 0.375% bleach solution using standard 6% sodium hypochlorite bleach – Clorox or the like.  You may also see this referred to as a ratio.  This is a 1:16 bleach solution because there are 16 tbsp in a cup.  1:9 is often recommended (and confusingly referred to as a 10% solution because 10% is bleach, even though the bleach you start with is a 6% solution to start with), but I think that is overkill. 15. Soak the seeds in the bleach solution for 10 minutes.

The bleach soak should help to destroy pathogens on the exterior of the seed and may also help to break down any remaining gel.

16. (Optional) Soak the seeds in water at 122 degrees F (50 C) for 25 minutes.

If you have the equipment to do so (a hot plate and a thermometer), you can heat treat the seeds.  This can help to kill pathogens (primarily viruses, since very little else will have survived the TSP and bleach).

I don’t bother with the heat treatment, but if you have reason to be concerned about seed borne viruses or are selling your seeds, you might consider this.  If you don’t have a heater that holds a steady temperature, you can damage your seeds pretty easily.

17. Rinse the seeds under warm water.

18. Let the seeds drip dry for a little while and then dump them on some paper to dry.

Try to spread them out some so that they don’t clump together. It will probably take a week or two for them to dry.

19. Store your seeds in a bag or a jar, preferably with some desiccant.

They’re still not as dry as they can be, so it is best to use a container that can breathe or to add a desiccant pack to dry them out further.

That’s it!  This may seem like a lot of work (and it can be if you are maintaining a lot of potato varieties) but potato berries generally give a lot of seed and it remains viable for a long time, so you probably won’t have to do this for every variety every year.

2 Responses to Potatoes: Extracting true potato seed

  1. laurieb October 1, 2013 at 7:46 am #

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  1. Potatoes: Growing from Seed (Part 2) | Cultivariable - September 23, 2015

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