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!)
Not every tuber has to be sprouted before it goes in the ground. Here is how the three cases you are likely to have on hand differ.
Which potatoes need germinating, and which don’t
Type of potato
Needs pre-germinating?
What to do
When to start
Pre-germinated potatoes bought in a horticulture store
No
Plant as they are, they are already ready
As soon as the soil averages 55°F (12°C)
Ungerminated tubers bought in shops, even a grocery store
Yes
Single layer in a shallow crate or egg tray, exposed to light
4 to 6 weeks before planting out
Tubers saved from your own harvest the previous year
Yes
Store cool and ventilated over winter, then sprout them in the light
Late winter to early spring
In every case the tubers are ready to go out once the sprouts are a few inches long.
How to germinate potatoes
This is the most successful way to help your potatoes germinate before planting:
One single layer, in a crate or egg tray
Use 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.
Sprouts of a few inches mean planting time
It’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
Transfer out once soil averages 55°F (12°C)
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 late winter-early spring, 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!
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 hiber
Sprouting tubers are at their most vulnerable stage
nating 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:
