If you consider yourself more of a “foodie” and less of a “gardener” because you don’t like the idea of getting your nails dirty, read on!
You can grow lettuce, greens, and herbs year-round in a hydroponic planter made from a repurposed coffee container.
Before you start questioning how difficult it must be to make a hydroponic planter, stop!
I want to share with you instructions for creating a specific low-tech hydroponic planter that uses no electrical pumps or air stones to circulate the water.
I’m referring to the Kratky Method of the “Non-Circulating Hydroponic System,” which is pure genius.
Developed by B.A. Kratky at the University of Hawaii, the simple hydroponic planter works on this premise:
(This explanation is from the “Three Non-Circulating Hydroponic Methods For Growing Lettuce” article on the University of Hawaii website.)
A non-circulating hydroponic concept for growing lettuce is described where electricity and pumps are not needed and the entire crop can be grown with only an initial application of water and nutrients.
At seeding or transplanting time, the growing containers are supported by the tank cover with their lower portion being immersed in the nutrient solution.
This moistens the growing medium in the containers by capillary action, thus automatically watering and fertilizing the plants.
Plant growth causes the nutrient solution to lower and creates an expanding moist air space and an expanding root system.
The main function of the roots in the moist airspace above the nutrient solution is aeration whereas the roots extending into the nutrient solution absorb water and nutrients.
WHAT IS HYDROPONICS?
- Hydroponics is a system of growing plants in water without soil.
- Plants receive their necessary nutrients through the hydroponic fertilizer that’s added to water.
- The plant roots are stabilized in clay pellets or perlite, coconut coir, or rice hulls instead of soil.
HOW DOES A COFFEE CONTAINER TURNED HYDROPONIC PLANTER WORK?
Take a look at my transparent demonstration model, but don’t use a clear container for your project.
It will allow light in and encourage algae to grow!
The coffee container is filled with “nutrient water” (water + liquid fertilizer) all the way up to the top.
One gallon of nutrient water per plant is an optimal ratio when growing lettuce, so use the right size container.
The water covers and soaks the bottom 1/4 inch of the net pot that’s filled with clay pellets that support the young lettuce plant.
As the water recedes, the plant roots continue to grow down looking for water and picking it up, as needed.
The space between the water and the bottom of the net pot is filled with humid air which provides oxygen to the roots.
When the water level drops to the bottom (after approximately 30 days), the lettuce plant is usually full grown.
You can grow another lettuce plant in this container!
Some people call the Kratky Method the “wet it and forget it” planting system.
LIGHT REQUIREMENTS FOR GROWING LETTUCE
Lettuce is a cool-season plant, so it can grow outdoors in mild winter areas in an area that receives a full day of sun.
Indoors, place your container by a bright window or use a fluorescent bulb for 10 hours if you don’t have natural light available.
Here is what you need to make your coffee container a hydroponic pot.
MATERIALS TO MAKE A HYDROPONIC PLANTER
- 33 oz or larger opaque coffee container. Don’t use a clear container as the light encourages algae growth
- Hydroponic “net pots” in 2-inch and 3-inch sizes.
- Liquid plant food
- Filtered water
1. Use a 2-inch or 3-inch net pot as a template for cutting a hole on top of the coffee container cover.
2. Cut out hole and insert the net pot.
3. Fill the coffee container with 1 gallon of filtered water and add 2 teaspoons of hydroponic plant fertilizer, then stir.
4. Place the coffee container cover (with net pot in it) on the container and put a lettuce plant in it.
Which brings you to the question of how can you grow lettuce seedlings without soil?
MATERIALS TO GROW LETTUCE SEEDS
- Rock wool cubes
- Salad bar container with plastic cover or seedling grow tray
- Clay pellets called “Hydrotone”
- Wood toothpick
INSTRUCTIONS FOR GROWING SEEDS WITH NO SOIL
Soak the rock wool cubes in water for 10 minutes to absorb water.
Use the end of a wet toothpick to pick up lettuce seeds and drop 2 per hole in rock wool.
Cover the small hole with a piece of paper towel.
Place rock wool in a seed tray or in salad bar tray and cover with a plastic top to create humidity.
Set tray on top of a warm appliance (TV, microwave) or on a grow mat for 1- 12 days and check daily for growth and humidity.
Once the seedlings have a few leaves on them, you can put them in a small net pot, stabilize with clay pellets and put the pot in your special repurposed coffee container/hydroponic planter!
Set your hydroponic lettuce plant near your sunniest window and supplement with fluorescent lights for 10 hours per day if in a dark room.