What it shows
A waste bottle can hold soil and a living plant. Drainage holes let extra water out so roots do not rot.
The science
Roots need both water and air. If water cannot drain, roots sit in water and rot. Holes at the bottom let extra water out. Plants also need sunlight and regular water. Growing herbs at home saves money and cuts waste.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- One empty plastic bottle of 1 or 2 litres (free)
- Soil, a handful or two
- Seeds of coriander or tulsi, or a small cutting
- String, 1 metre
- Scissors and a nail for holes
- Paint or paper to decorate
Safety
For this project: An adult must cut the bottle and make the holes with a nail.
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.
Step 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.
Ask an adult to cut a window in the side of the bottle, leaving the neck and base.
Make four small holes in the underside of the bottle, opposite the window, for drainage with a nail.
Make a hole near the neck and another near the base on the top edge, tie a string through each and join the two strings above, so the bottle hangs level with the window facing up.
Fill the bottle with soil up to the cut edge.
Sprinkle coriander seeds on the top and cover with a thin layer of soil.
Water gently until the soil is damp but not soggy.
Hang it in a place with morning sun.
Water daily and draw the plant every few days.
What you should see
Seeds sprout in about a week and you grow fresh coriander in a hanging bottle.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01Why make holes in the bottom?
So extra water drains out.
02What do plants need to grow?
Light, water, air and soil.
03Why reuse a bottle?
It cuts plastic waste.
04Which herb did you plant?
Say your choice.
Take it further
Hang three bottles in a row with different plants and compare growth.
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.
Free ebooks for this project
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