How are your potatoes? Share photos, questions, comments! Here is a guide to support your process. I’d love to hear how you are doing it.
Last month I wrote a blog post about about selecting your best tubers and replanting them. Here is a link if you missed it or want a review.
Curzio recommends that in the first year of growing from true seed, don’t save the berries from the plants, since you don’t know what you’re going to get when replanting in future years. Save several tubers from each plant to replant the following year in your own garden.
Photo showng tubers and berries saved from a second year after planting from true seed.
Sending Seeds to Going to Seed: If you have been growing from true seed for at least a year, and have a tried and true plant that’s producing berries, we’d love them! Due to potential male sterility issues, we can’t automatically accept berries from commercial varieties. If you’re unsure and want to contribute, I’d love to hear from you, julia@goingtoseed.org.
How do you know when it’s time to harvest tubers?
Plants grown from seeds tend to live a lot longer than tuber-grown plants, so it can be tricky to know when to harvest. But in general, once a plant has formed berries, the tubers are also ready. So wait for those flowers to turn into berries, then start harvesting. If you have no flowers, or they fall off without berries, wait for the plant to turn yellow, and check the soil around it for tubers.
Prepare to harvest by not watering for 2 weeks before you dig up the tubers (or stop irrigating after the flowers drop). The tubers will cure and form good skins best for storage in dry soil.
Once you’ve determined any of your plants are ready, proceed to the next step 
Two harvest options to choose from:
First Option: Harvest everything together
- Harvest everything at once when most of the plants are ready. Determine how many tubers you want to save to replant the following year, and separate those.
- Eat the rest!
Even though this might sound too simple, it’s what Adaptation Gardening and ‘Evolutionary Plant Breeding’ are based on, ancestral and Indigenous techniques that form the basis for how humans domesticated plants: The healthier plants will produce more tubers, so each year you do this, your potatoes will move towards a population that yields well and thrives in your garden. You can adjust this by harvesting everything together and then favoring tubers for replanting by choosing your favored colors. You may come across an occasional bitter potato (2% or less), in which case don’t eat it, and don’t replant any other tubers that look like it (from the same plant).
Second Option: Select Plant-by-Plant
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Bring a crate for all the potatoes you’re going to eat, and enough separate bags or boxes for the rest of your plants. Seed-grown plants will mature at different times, so you can dig the ones that are ready now, and come back in a few weeks to harvest the rest.
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Loosen the soil with a digging fork and pull up the roots and tubers, one plant at a time. Add at least three tubers from each plant to your separate bag or box. Small paper bags (sandwich bags) work well for this, keeping them separate until you replant in the spring.
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Add the rest of the tubers from that plant to your ‘eating’ box. If you find a fantastic harvest, I still encourage you to save some berries from that plant to replant the following year in your garden. Your tubers from this plant may get damaged, sprout too early, rot, or not grow, so it’s good to have seeds as well that will store for years.
Proceed plant by plant, saving a few tubers separately from each plant. -
Taste Testing: Keep the tubers separated, and one tuber from each plant. Discard anything that is bitter or isn’t delicious (for you).
Video: Joseph Lofthouse and Julia harvesting potatoes plant by plant in 2021
Selection Notes:
Even if the plant has died from blight or anything else, it should be evaluated based on the tubers it produced, and not what the plant looks like at the time of harvest. You can easily have a giant and beautiful green plant that produces zero tubers, and a plant that has died, that had produced plenty of tubers. The first method of harvest (saving everything together) will automatically account for this.
Personal preferences: If you have enough tubers to be somewhat choosy, feel free to make some choices before separating into sandwich bags. For example, I love tubers that are pink, purple, and dark yellow. At each plant, I cut open a tuber, and when I find white-fleshed potatoes, I add all the tubers from that plant to my eating box, and some berries if they plant is also especially productive.
Storage: For long-term storage, tubers need cool temperatures (ideally under 55F), airflow, darkness, and high humidity Putting some in your refrigerator can be the most secure, microtubers from your best plants don’t take up a lot of space. Put them a paper bag, in the produce drawers, and of course mark them very obviously so you don’t end up eating them for breakfast, lovingly cooked by somebody in your household.
Saving Seeds
So, you have some favorite plants and are ready for the next step:
Wait until the berries have matured as much as possible from your selected plants. They should be the size of small cherry tomatoes. They may fall off the plant, so to ensure you know which berries come from a specific plant, you can add a mesh bag around the cluster.
Allow the selected berries to ripen further off of the plant, in a protected place with light. Unless you have a good reason to keep different plants’ berries separated, I recommend combining berries at this point, ensuring that you have a good mix of colors and not allowing any single plant that produced a ton of berries to dominate your mix.
Post-ripening process: Allowing them to mature past the green phase (they may turn soft whitish) will increase the seed quality, germination and viability. Ideally give them a natural place to mature, for example on soil and leaves. Keep them from drying out– mist them occasionally. Don’t leave them in a plastic bag where they can get moldy or ferment prematurely. Even if they stay green, they will still be viable, but the riper the better. Don’t allow them to rot or dry out.
Once they are soft and mature (could be 2-4 weeks), you can process them for seed.
Cut the berries in half and add to a glass jar. Fermenting the seeds makes them clean and easier to handle, and removes their germination inhibitor. Squish them up to remove air, as you would when fermenting vegetables for kraut. Cover the jar with a paper towel and rubber band to protect from fruit flies and smell (they do need airflow!). Let this mixture ferment for 2-4 days until a white mold forms on top, similar to tomatoes. Don’t forget about this mixture, because letting it get too acidic (happens after 3-4 days), reduces future germination, or causes seeds to sprout.
Cleaning the seeds: Add fermented berries to a larger container and add the same amount of water. Agitate thoroughly to separate the seeds from the pulp. I use a blender on a low setting for about ten seconds. Potato seeds are hard and tiny and won’t be damaged as long as you don’t have the blender on high. Once seeds are freed from the berries, add more water.
The seeds will sink to the bottom, and debris will float to the top. Pour off everything but the seeds, and repeat this process several times, carefully pouring off whatever is lighter than the seeds.
Once you have only seeds and clean water, pour seeds into any very fine mesh screen or tea strainer, and dry on a paper plate or screen.
Dry the seeds for a few days anywhere with good airflow. If you don’t have such a place, you can use a dehydrator set to under 90F. Keep them out of direct sunlight, and if you put them outside protect from wind and critters. Depending on airflow and temperature, they may take 2-7 days to dry. Break up clumps during drying, mix, and keep drying.
Storage: Once completely dry, break up any clumps and store in a cool, dry place in labeled envelopes or jars. Add a silica or clay packet to absorb any excess moisture during storage. Avoid storing damp seeds because mold will make most of your seeds non-viable.
