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Plants come in all shapes and sizes, from giant oak trees to tiny flowers. Some have bright and colourful flowers, whilst others have leaves that turn red in autumn and fall off. No matter what the shape and size, all plants need the following things:

• air
• light
• water
• nutrients
• the right temperature

If plants do not get the correct amount of these five things then they will not be healthy and might die. If they do not get the right amount of sun, they won't get the right amount of nutrients. Unhealthy plants turn brown and wilt.

We can spot healthy plants because they normally stand upright and are green. They continue to make their own food in their leaves by photosynthesis.

To look after plants, we need to provide them with the right amounts of light, water, temperature, nutrients and air.

Why not carry out your own science experiment using cress or sunflower seeds!

You will need: damp cotton wool or toilet paper, two dishes and some cress or sunflower seeds.

1. Put some wet cotton wool or toilet paper in the bottom of two dishes and sprinkle the seeds on top.
2. Decide the variable you want to investigate. It could be light or water.

• If light, add the same amount of water to both dishes and place one in the sun and another in the shade.
• If water, add only a very small amount of water to one and more to the other. Place both in the sun.

3. Wait for two weeks and see which one grows best.