The Absolute Beginner’s Guide to True Potato Seed (TPS)

There is a lot of information on this website about growing potatoes from true potato seed, but I often hear from people who are interested but who don’t have the time to read all of that material.  If you have heard about TPS and are wondering if it is something that you would enjoy trying out in your garden, this should help you to make the decision.

If you have grown potatoes before, you probably started them from tubers. Somewhat confusingly, we call the tubers that you plant “seed potatoes.”  The potato plant also makes actual seeds, which we call “true potato seeds” or just TPS.  Seed potatoes are no different than the potatoes that you eat, with the exception that they are usually grown by specialist seed potato growers who pay particular attention to managing disease, since potato tubers can carry a lot more diseases than crops grown from true seeds. In contrast, true potato seeds come from the berries of the potato plant.  The berries form when potato flowers are pollinated.  Many people have never seen berries or even flowers on their potato plants, for reasons tied to climate and cultivar. 

Why not just grow potatoes from true seed then?  That’s the tricky part.  Potato varieties are clones.  When you plant a tuber of, say, Yukon Gold, you are really planting part of the same original plant that was first grown in the 1970s.  Each generation of tubers is just more clones of that plant.  Clones are predictable, which is a good thing for agriculture.  True potato seeds, on the other hand, are the sexual progeny of the potato plant and, just like human children, each one is different.  Every seed in every berry will produce a plant that is new and distinct from any other potato; it is a brand new variety with newly jumbled up genetics.  That potato is unique to your garden.  When you grow potatoes from TPS, you are breeding new varieties.  Even if you are only growing out seeds produced by someone else, you get to choose which varieties to keep and which to discard, based upon what matters most to you.  You can keep them and replant the tubers indefinitely.  You can name them, share them, or even sell them if they are particularly good.

Seed Potatoes vs. True Potato Seeds

Seed Potatoes True Potato Seeds
Tubers are genetic clones of the parent plant Seeds are genetically unique progeny
Results are predictable and uniform Results are unpredictable and diverse
Tubers can be planted directly in the soil Seeds are started indoors, similar to tomato
Tubers can carry a lot of diseases Seeds carry few diseases
Tubers last about a year Seeds can last 50 years in the freezer
Selection is limited, with less than 100 varieties available commercially Selection is very wide, with access to many unusual types

When you grow potatoes from true seeds, you will usually get a wide range of results.  Some plants may produce nothing, while others can produce a tremendous yield.  Most will be somewhere in the middle.  Depending on what seeds you start with, you may get unusual colors and shapes that you would never find at the grocery store.  Most of the seed potatoes that are available to gardeners are the same varieties that are used in large scale agriculture.  They tend to be optimized for best production in potato growing regions and they have traits that best suit growers and processors, rather than consumers.  If you live in potato country and you are totally happy with grocery store spuds, TPS might not be for you.  You aren’t likely to get better varieties with commercial traits than the ones that already exist.  On the other hand, if you are trying to grow potatoes in an area where the commercial varieties don’t do very well or you find grocery store spuds a little dull, TPS is probably just what you are looking for.  Just have a look at the kinds of results that we get from our true potato seed mixes:

Mixed red tetraploid potatoes

High dormancy diploid (Stenotomum type) potatoes

Potatoes from Cultivariables 2018 wide diploid TPS mix

High dormancy diploid (Stenotomum type) potatoes

Mixed red tetraploid potatoes flesh colors

Mixed tetraploid potatoes flesh colors

Potatoes from Cultivariables 2018 wide diploid TPS mix

Potatoes from Cultivariables 2018 wide diploid TPS mix

There is incredible depth to the potato.  If you are looking for something that you can grow in your garden that will never show you the same thing twice, you would probably enjoy TPS.  If you have only been exposed to grocery store potatoes, you have barely scratched the surface.  TPS gives you access to a whole new dimension of flavors, colors, and textures available in Andean potatoes and there are also nearly 100 species of wild potatoes, many of which can be crossed with domesticated potatoes to introduce new traits.  The process of growing potatoes from true seeds can seem intimidating, but if you can grow tomatoes from seed, you can grow potatoes from seed.  There are some common mistakes to avoid when growing TPS, but once you get past those, growing potatoes from seed is easy.  If you find it interesting, you can also get very deep into the technical details of potato breeding and learn more than you ever imagined.  You could probably spend a lifetime exploring potatoes from TPS and never get bored.  I could, anyway.

The easiest way to get started growing potatoes from TPS is to start from seeds.  If you are in a favorable climate, you might be able to save seeds from potatoes that you already grow, but this is a bit tricky for most people.  The plants that you grow from TPS are much more likely to form berries than plants grown from commercially available seed tubers.  Once you get started, you can easily save your own seeds and keep growing.

Start your seeds in flats or pots no more than eight weeks before your last frost.  For most people, it would probably be best to start them four weeks before the last frost to keep from planting them out too early.  Grow them under lights.  Ambient light is not enough for potato seedlings.  Keep the temperature between 50 and 70 degrees.  Too hot or too cold and they will be slow to emerge.  When the seedlings are about six inches tall, harden them off and then transplant outdoors, burying them up to the top set of leaves.  You can make starting TPS more complicated than that, but for your first attempt, it should work just fine.

You can buy many kinds of true potato seeds in our store.  For absolute beginners, I recommend the Wide Tetraploid True Potato Seed Mix.  If you are ambitious, there is a lot more available at our true potato seed page.

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3 thoughts on “The Absolute Beginner’s Guide to True Potato Seed (TPS)

  1. Justin Songwe says:

    How long should the berries stay on the potato plant after they’ve formed and when should they be harvested

    • bill says:

      The berries should be left on the plant at least six weeks. It is even better to leave them until they fall off on their own or can be removed with just a light touch, although they may be vulnerable to animal damage if you leave them that long.

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