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Hydroponic experiments for kids

Below are some very inexpensive classroom projects. The experiments are meant as a fun introduction to hydroponics. We suggest that anybody new to hydroponics start with the 'soda bottle' experiment.

They will learn what you feed a plant matters more than what the plant grows in.

  • The project involves simple math (mixing nutrient).
  • The student can write down growth observations on a report with drawings of what they see and do. (English)
  • They learn that you don't need soil and that plants needs food and oxygen. (Biology)
  • The experiment only requires the purchase of some hydroponic nutrient, the rest the kids can bring from home.
  • It is ideal for schools new to hydroponics. The students will thrill over the experiment, while the educational value will help convince the school board to consider hydroponics for the curriculum.

Plant for all experiments:
We suggest Swedish Ivy /Creeping Charlie. This plant seems to grow no matter what - we even rooted this one in a coconut pound cake ! The roots will set from the nodes. Put the cuttings in a glass of water and wait for roots to appear (aprox 2-3 weeks), then take them to your classroom. This way the students do not have to wait very long for the plants to start growing.

‘Shopping’ list.
Empty 2 liter soda bottle, wick, fertilizer, plant, lemon or lemon juice, baking soda. Optional: pH test kit or litmus paper, straw, Lego blocks, shredded fabric, shredded paper.

Other materials:
You need liquid hydroponic nutrient. Typically you only use 1-2 tsp per gallon, so a bottle goes a long way.
Each Soda bottle will also need a wick. You can purchase proper wicks or the students can bring in pieces of a cotton T-shirt. It could even be put to the student to find which fabric will be the best wick.
You will also need baking soda and lemons (or lemon juice). This is used to adjust the pH, so the plant can grow. Plants grow only between pH 5 and pH 7.
It would be helpful for you to buy a little pH test kit/ litmus paper- or you can ask the hydroponic store if they know what the pH is of your local water. If the pH is over 7: add ½ squeezed lemon per gallon water. If the pH is 5 or lower (unusual), add 1 tsp baking soda.
Ask each student to bring in an empty soda bottle and possible wick material.

General for all of the following experiments:
The soda bottles should have the top cut off and put back in the bottle up side down, as shown in the photo. The liquid the plant will be growing in should always be pH adjusted. If your tap water is fine, then adding the nutrient will not change the pH so much that you have to adjust it. If you are letting the student bring in 'home made' wicks, we suggest that the water level in the bottle always touches the bottle neck (which now hangs inside the bottle). This way we are sure the water gets up to the plant.

Fun Experiments:

For each Experiment you need to choose:

  1. Growing media
  2. Plant food mixture (also called nutrient solution)
  3. What environment ? (Such as temperature, light, air)

Here are examples of the choices within each of the above 3 groups:



1. Growing Media

Lego blocks, Shredded Paper, Shredded fabric, Hay, Polymers see also: Experiments

2. Plant Food Mixture

Choices in this group are only limited by your imagination

Mixed according to the plant food bottle,

20% of mixture replace by Coca-Cola,

40% of mix replaced by Kool Aid,

10% of mixture replaced by Milk,

Using only plain water

Your own home made plant food mixture

3. Environment Light




No Light, Table lamp, Fluorescent light, Sun light.

Warm room, refrigerator, normal room temperature

Blow exhaled air on the plant, blow air with a bicycle pump.

Using a straw blow air into the plant food mixture in the soda bottle.

The upside down soda bottle top is referred to as 'the container' in the following. The remainder of the bottle is 'the reservoir'.


If you want to make good comparisons, then you need to take one specific choice from each of the two groups and then let the third group be your viable.

Two Examples:

(1) Goal: You want to see the effect of light.
Set up 4 bottles each with the same growing media and each with the same plant food mixture (and same plant) . Now expose each bottle to different light.

(2) Goal: You want to see which growing media works the best.
Set up 5 bottles. Put a different growing media in each ‘container’. Use the exact same plant food mixture in each of the 5 bottles. Place all 5 bottle in the same place/same light.

Classroom Experiments

(Add nutrient solution, wick and plant)
Use Lego blocks as growing medium in the container.
Use shredded fabric as growing medium in the container. Which kind of fabric works the best? Why do you think that is so?
Use shredded paper as growing medium. What works best leaflets, newspaper or your old essay?
Try using little rocks from the driveway as growing medium.

(Add growing media, wick and plant)
Regular solution as recommended on the reservoir.
Replace 20% of the nutrient solution with Coca-Cola - add baking soda to adjust pH.
Let the kids make other suggestion to additions to the nutrient solution; such as milk, orange juice, Kool aid, coffee... Be sure to check that the pH is around 6.

Let kids blow air into the water in the reservoir at a regular interval. Do these plants do better than the other plants (with increasingly stagnant water...)
What if you blew air on the plant? Does it make a difference? (It might, since the plant gets more CO2)
Temperature - does it matter?
Sun light, no light, light from fluorescent light, light from a table lamp: what works best?
You can now make many experiments with any combination of the 3 groups. Example: Grow the plant in Lego blocks. Add milk to the nutrient solution and see if the plant can grow without light.

Once the classroom media have been tried in the bottle experiments - then consider continuing with some regular hydroponic growing media such as Grodan Grow-Cubes™, Clay pellets and Coir

The local hydroponic store can help you with ideas and system set up. You will find all the stores listed on grodan101.com.