How to Grow Potatoes in Water

A potato will sprout in plain water, but it won't produce a crop. In water, a potato lives on its own stored energy to make shoots and roots. To grow new potatoes, the plant also needs nutrients, light and a dark place for tubers to form. A Kratky container provides all three.

Sprouting a potato in a jar of water

This is the classic kitchen project, and a good way to watch roots form.

1. Pick a firm potato with visible eyes. Seed potatoes and organic potatoes sprout most reliably, because some supermarket potatoes are treated to stop sprouting.
2. Push three or four toothpicks into the middle of the potato and rest them on the rim of a jar, so that the bottom third of the potato sits in water.
3. Put the jar somewhere bright but out of hot direct sun.
4. Change the water every few days, or sooner if it turns cloudy or smells.
5. Roots and shoots usually appear within one to two weeks.

What plain water can't do

Once the potato has used up its stored starch, growth stalls. Plain water has no nitrogen, potassium or other nutrients, so the leaves turn yellow and no new tubers form. The part of the potato under water also tends to rot after a few weeks.

Moving from water to the Kratky method

When the sprouts are a few inches long, you can move the potato into a Kratky container: a deep, opaque container of hydroponic nutrient solution with a net pot or basket in the lid. The potato sits in perlite or coco coir above the solution rather than in it, and new tubers form in that dark medium. As the plant drinks, the solution level falls and leaves an air gap that gives the upper roots oxygen.

Questions about growing potatoes in water

Can you grow a whole potato plant in just water?

Not to harvest. Plain water supports sprouting and early root growth only. For tubers, the plant needs nutrient solution and a dark root zone.

Do potatoes grown in water need nutrients?

Yes, once they move past the sprouting stage. A complete hydroponic nutrient supplies what soil would.

How often should I change the water?

In a sprouting jar, every few days. In a Kratky container you don't change it: you let the level fall and top up only a little when needed.

Can I plant a water-sprouted potato in soil?

Yes. Once the roots are a few inches long, plant it with the sprouts just below the surface and handle the roots gently.

Why is my potato rotting in the water?

Usually too much of it is under water, the water is stale, or it's too warm. Keep only the bottom third in water and change it more often.

Can I eat potatoes grown this way?

Tubers grown in a Kratky container are eaten like any other potato. Don't eat green parts, and don't eat the old seed potato after it has sprouted.