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Germinating potatoes at the right time

Germinated potatoes chopped up in quarters for more plants.

Germinating potato tubers before planting them helps increase growth of your young plants. It brings the harvest a few days or weeks earlier, and increases harvest size and quality.

This technique doesn’t apply to “pre-germinated” potatoes purchased in horticulture stores. Pre-germinated potatoes are already ready to plant.

Potato germination applies to:

  • tubers purchased ungerminated (even from grocery stores!)
  • and potatoes harvested during the previous year

This works for all potato varieties, from the black vitelotte to sweet potato!

How to germinate potatoes

This is the most successful way to help your potatoes germinate before planting:

  • Tray to germinate potatoUse a shallow crate or an egg carton/egg tray.
  • Line the potatoes along the bottom, only a single layer.
  • You don’t need soil or anything, though a piece of carton or rumpled newspaper underneath helps regulate moisture and temperature.
  • If a bud is already present, turn it so it faces upwards.
  • Expose the potatoes to light in a dry, cool and well ventilated place.
  • Ideally, the temperature should hover between 40°F and 50°F (10°C to 15°C).
  • Potatoes take around 4 to 6 weeks to germinate.

Germinated potatoIt’s normal for the potato to wither and wrinkle.

This is because nutrients are converted into sprouts and roots.

When the sprouts are a few inches long (5-10 cm), the germinated potato is ready for planting.

Some of the sprouts may die off or their tips might turn black. This is usually a sign that you shouldn’t wait too long before planting.

Using your own potato plants for germinating

Germinated potato being planted in the ground.It is perfectly possible to germinate spuds from last year’s potato harvest.

  • It’s important to pull these future “seed potatoes” out about 4 weeks before the potato harvest.
  • Choose potatoes that are not diseased and come from vigorous plants.
  • Let them sit on the ground for a few days.
  • From these tubers, select those that look nicest, with no sign of rotting. Eat the others!
  • Store them in a cool and ventilated space until next spring.
  • Around February-March, launch the germinating process as explained above.

A few weeks after your potatoes have begun to germinate, outside soil should be averaging temperatures of around 55°F (12°C). It’s time to transfer them to the ground and grow your potatoes for a beautiful harvest!

Pests that eat germinated potatoes

Potatoes that are germinating are at their most vulnerable stage. Their skin is pierced by growing buds, sometimes creating wounds that pests and fungus can enter through.

Also, spring temperatures are warming the soil, waking hiberUnderground potato pestsnating insects from their slumber. Regular earthworms won’t eat your potatoes, so nothing to worry about there.

Here are the main culprits eating potatoes underground:

Note: the colorado potato beetle is never a problem at this stage: all it damages is above ground.

Diseases that damage young potato tubers inclure blackleg and scab.

Smart tip about germinating potato

A good way to know the right timing for planting is when buds start turning a bit purple…

Lacking a  few to finish off the row? Slice a larger one in half with a bud on each side. Plant each half separately.

Images: CC BY 2.0: Ivan Radic, Sami Sieranoja; own work: Rosalyn & Gaspard Lorthiois
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