Step 1: Pick a Kratky container

What you need

Kratky containers can be almost anything that holds water and keeps out light.

A dark container that holds water, a lid or cover that blocks light, and a net pot for the plant.

Why dark?

Light makes algae grow in the water. A dark container keeps the water clean and the roots healthy.

Good Kratky containers

• Mason jars, wrapped in foil, paper or a fabric sleeve
• Food-grade plastic tubs with lids
• Buckets with lids, for larger plants
• Storage totes, for several plants at once
• Dark plastic bottles with the top cut off

Choose something clean, and food-safe if you can. Never use a container that once held chemicals or paint.

Glass or plastic?

Glass jars are easy to find and easy to clean, and you can lift the cover to check the roots. But glass can break if it falls, so place it somewhere stable.

Plastic is lighter and less likely to break. Dark or opaque plastic is even better, because it already blocks most light. Clear plastic needs a cover, just like a glass jar.

How to block the light

Wrap the outside of the container in aluminum foil, dark paper or tape, or slide it into a fabric sleeve or paper bag. Cover the lid too, except for the hole where the net pot sits.

A lift-up flap is handy: leave a narrow strip you can fold back to check the water level and the roots, then cover it again.

What size should it be?

Small leafy plants like lettuce, basil and other herbs do well in a jar. Bigger plants use more water, so they need a bigger container, like a bucket. If the container is too small for the plant, the water can run out before harvest. When in doubt, go a size up. More on Plants to Grow.

The lid and the net pot

The lid holds the net pot, and the net pot holds the plant. A net pot is a small slotted cup that lets roots grow through into the water. It should fit snugly in the lid so it cannot drop in. Wide-mouth mason jars are popular because a standard small net pot fits the opening.

If your lid has no hole yet, drill or cut one just big enough for the net pot to sit in without slipping through. Drilling plastic is safer than cutting it with a knife.

Get it ready

Wash the container and lid in warm, soapy water and rinse well. Leftover residue or soap can cloud the water. Once it is clean and covered, move on to Step 2: Add water and nutrients.

How many containers?

One jar is a good start. If you want to grow more than one kind of plant, use one container for each. A tote with several holes in the lid can hold many plants at once, but it is heavy when full and needs a strong, level spot.

Common container mistakes

• Using a clear container with no cover, so algae grows
• Using a container too small for the plant
• Making the lid hole too big, so the net pot falls in
• Skipping the wash before first use

Quick container checklist

• Holds water without leaking
• Blocks light on every side
• Big enough for the plant you chose
• Lid holds the net pot snugly
• Clean and rinsed

Why the Kratky container matters

The container holds all the water and nutrients the plant will use, keeps the roots dark and cool, and leaves room for the air gap. A good container makes every other step easier, so it is worth a few minutes to choose and prepare it well.

Food-safe materials

Since you will eat what you grow, the container matters. Glass, food-grade plastic and buckets sold for food storage are all good choices. Avoid containers that held cleaning products, solvents or paint, even after washing, and avoid soft plastics that may break down in sunlight.

If you are unsure, choose glass.

Containers for larger plants

Buckets and totes give large plants enough water to last until harvest. Choose an opaque one, or paint or wrap it so no light gets in, and make sure the lid sits firmly so it can support the net pots and the weight of the plants as they grow.