Step-by-step guide
1 First your children should place some crocks at the base of their plant pot.
2 Then they need to half-fill the pot with soil or compost.
3 Help them to dig up a dandelion. They must get most of the long taproot up with it, without which it will quickly die. (The taproot is the straight, tapering root growing vertically downwards and forming the centre from which subsidiary rootlets emerge.)
4 Help your children to plant it in the pot, and firm it in with more soil or compost.
5 Let them water it well, then put it on a windowsill.
6 Look at it regularly. They should see it grow buds, then the flowers will open, then they'll die, and finally the seed clocks will form.
7 Their dandelion should grow quite a few flowers. They can count how many it grows, then see if they can guess how many seeds it has produced - hundreds!

Useful information
Many plants are known as weeds because they are successful at growing where more delicate species would die. Dandelions are strong plants. In fact, the trauma of being dug up will actually stress the plant and cause it to produce more flowers, rather than killing it. Eventually it's likely to die in the pot.