Getting Started With The Kratky Method
Alex Langston 3.11.2021
One of the simpler, less expensive hydroponics solutions is a system called the Kratky Method. In 2004, Dr. Kratky published information about his method of suspending plants in a non-circulation nutrient solution. At a basic level, the Kratky Method is a container, or reservoir, of nutrient solution with a plant suspended above it so its roots are partially covered by the solution. There are no water pumps to power, no flow rates to manage, so it is a great way to introduce one’s self to hydroponics.
Mason Jar or other plastic/glass container
2” Net Cups
Aluminum Foil or dark paint
Plants of your choosing (Tomatoes are a great choice for beginners)
*The items in this list are suggestions. There are many possible variations on hydroponic systems, allowing for the use of a massive number of different supplies. Researching and customizing is all part of the fun!
Start your build with a clean jar or bucket that’s been blacked out with by either wrapping (i.e. foil, newspaper) or painting it. This is a critical step because roots can be damaged when exposed to too much light. If there is enough light for algae to grow in your nutrient solution, that will potentially damage roots, as well.
Suspending a net cup in jars with wider mouths can be tricky. Using a utility knife, cut an appropriately sized hole in something like cardboard or thin plastic. If the plastic you’re using is clear, it may need to be blacked out with paint, or foil once the hole is cut. Some of the more DIY hydroponic gardeners skip net cups altogether in favor of empty yogurt cups. They cut slits in the bottom for roots to grow through, then suspend the cup using the attached wings.
Once seedlings are tall enough to reach your light source from the inside of a net cup, carefully transfer them to an empty net cup, washing their roots (only required if your grow medium sticks to them). Add enough clay pebbles to hold the plant in place and block light from passing through to the nutrient solution.
Set the net cup so the plant’s roots hang down into the jar of nutrient solution. You’ll want your container just full enough the roots are partially submerged. Since the Kratky Method doesn’t have an air pump to add oxygen to the nutrient solution, plants get their oxygen from the air around them. As the plant takes up water and nutrients and as the solution evaporates, its roots will grow along.
Caring for Your Plants
As soon as your plants are suspended safe and sound over the container of nutrients, you can place them in a sunny window, or under a grow light. Depending on the amount of shock the plant is experiencing, it can be best to be gentle on it until symptoms subside. If it is a plant that eventually requires full sun, maybe allow it a little extra time in the shade until it looks full strength.
Different types of plants require different amounts of nutrients, and will consume them from your solution at varying rates. Flushing old solution once in a while replenishes those nutrients and prevents deficiencies.
Some things to be aware of as your hydroponic experience advances are the pH of your nutrient solution, the quality of the water you use in your reservoir (the jar in this case), and a few common nutrient solutions. If you can block out light well and are checking on your plants once in a while, that’s enough for most of the veggies that will grow well in Kratky systems.
A Note on Soil
There are more detailed articles on starter medium, but something important to keep in mind is using soil to start your plants introduces the risk of transferring diseases into your hydroponic system, which could put other plants in danger in solutions involving multiple plants. There is also a period of shock a plant goes through upon being transferred that can delay growth and potentially kill a plant.