Kratky Problems

Most Kratky problems have a few simple causes

Kratky problems are rarely mysterious. A Kratky container has no pump, no timer and no moving parts, so when something goes wrong it usually comes down to a short list of causes: light reaching the water, water that is too warm, an air gap that is too small, roots that no longer reach the solution, or nutrient strength and pH that are off.

This page is the starting point for troubleshooting. It lists the checks in the order that finds the cause fastest, then links to a page for each common problem.

Check these in order

• Roots and water level: do the lower roots still reach the solution, and is there an air gap above it?
• Light on the plant: is the plant getting enough light, or is it pale and stretching?
• Light on the water: can any light reach the solution through the container, lid or gaps?
• Heat: is the container in hot sun, near a heater, or in a warm room?
• Nutrients and pH: was the nutrient mixed at the label rate, and is the pH in the range the label recommends?

Most of the time, the first or second check finds the problem. Fix one thing at a time, and note what you changed, so you can tell what worked.

Algae: green growth in the water

Green or brown film on the container walls, net pot or clay pellets means light is reaching the solution. Algae competes with the plant for nutrients and oxygen and can coat the roots. The fix is to block the light completely. Algae in a Kratky Container explains how.

Root rot: brown, slimy roots

Healthy Kratky roots are white or cream and firm. Brown, slimy roots with a bad smell are a sign of root rot, which usually starts in warm water or when the upper roots have no air gap. Kratky Root Rot covers the causes, what to do and how to prevent it next time.

Yellow leaves

Yellow leaves have several possible causes, from normal aging of the oldest leaves to weak nutrient, pH out of range or too little light. Where the yellow appears is the best clue. Yellow Leaves on Kratky Plants walks through each pattern.

Mosquito larvae outdoors

Outdoor Kratky containers hold still water, and mosquitoes look for still water to lay eggs. Small wriggling larvae in the solution mean there is a gap they can get through. Mosquito Larvae in a Kratky Container explains how to keep them out.

Problems that are not problems

• The water level dropping: that is how the method works. The plant drinks the water and the air gap grows.
• Roots that look different at the top and bottom: upper roots in the air gap are often finer and fuzzier than the lower roots in the water.
• A few lower leaves yellowing late in a grow: older leaves often fade as the plant puts its energy into new growth.
• Fine white fuzz on the upper roots: roots in humid air often grow fine root hairs. Slime and a bad smell are different, and point to rot.

When to start over

Some problems are faster to fix with a fresh start than with a rescue. If the roots are mostly brown and slimy, if the solution smells bad, or if the plant has wilted and not recovered, empty the container, wash everything in hot soapy water, rinse well and plant again. A clean container, cool water and a dark lid solve most repeat problems. The six steps in Make a Kratky Garden cover the setup.

How to prevent most Kratky problems

• Use a fully opaque container, or wrap it so no light gets in
• Cover any gaps around the net pot
• Keep the container out of hot afternoon sun and away from heaters
• Fill only to the bottom of the net pot, and never top up to the brim
• Mix the nutrient at the label rate and check the pH after mixing
• Wash containers, lids and net pots between plantings

Each of these is covered in the step pages, starting with Step 1: Pick a container.

Keep a short problem log

When something goes wrong, write down the date, what you saw and what you changed. Add the nutrient amount and the pH whenever you mix or top up. After a few grows, the log shows patterns that are easy to miss day to day, such as problems that only appear in summer or in one spot in the house.