What it shows
A wick moves water from a reservoir into the soil by capillary action. A plant in a wick pot stays healthy while a normal pot dries out, which shows how to save water and look after plants during holidays.
The science
Water rises through the fine gaps in cotton fibres by capillary action. Soil also pulls water from the wick as it dries, so the supply is automatic. The plant takes the water it needs, and the reservoir lasts for days.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Two plastic bottles cut in half
- Cotton rope or strips of old cloth
- Potting soil and two small plants or bean seeds
- Water
- A ruler
- A notebook
Safety
For this project: An adult must cut the bottles. Wash hands after handling soil and keep the pots on a stable shelf.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Cut the bottle and turn the top part upside down to sit in the lower half as a pot.
Thread the cotton wick through the neck so that about 10 cm hangs inside the lower half.
Fill the upper part with soil, keeping the wick buried in the middle.
Pour water into the lower half until the wick tip is covered.
Plant the seeds or seedling and place the pot in the light.
Make a second pot with no wick and water it from the top once at the start.
Check the soil dryness and the plant every two days.
Record how many days each plant stays healthy and note the water used.
What you should see
The wick pot keeps soil damp for many days while the normal pot dries and the plant wilts. The notes show how long the reservoir lasts.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1How does the wick work?
Water climbs up its fibres by capillary action.
2Why is a control pot used?
To compare with a normal pot.
3Where is this idea useful?
For balcony gardens and when we are away.
4What limits how long it lasts?
The size of the water reservoir.
Take it further
Compare wicks of cotton, nylon and jute and see which moves water best.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
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