Make sure, though, that children realise that annual plants are short-lived so they're prepared for the plant to come to the end of its life.
Choose plants with lots of colour, like petunias; hardiness, like marigolds (although some children don't like their smell); good smells, such as sweet peas; or shade tolerance, like impatiens.
Nasturtium seeds are relatively easy to handle and the plants are also straightforward to cultivate. They make a good choice for container growing or garden beds.
If it is difficult to grow a pot outdoors, hardy indoor plants, like peace lily (Spathiphyllum sp.), arrowhead (Syngonium sp.) or a kentia palm (Howea sp.) can be placed in a well-lit spot, out of direct sunlight, in a child's bedroom and even given a name.
Teach the child to judge when the plant needs watering by feeling the top of the potting mix, or by using a self-watering pot. Make sure that the water can drain away and that the roots are not sitting in moisture all the time.
If necessary, put a layer of fine pebbles in the saucer — this will raise the base of the pot above the residue of water in the saucer.