Mustard or radish seeds can be planted on a wet sponge placed in a dish. Here is one child's record:Home page
Day 1 - Yesterday we planted mustard seeds on a sponge in a dish. The seeds are yellow.
Day 2 - Little roots can be seen.
Day 3 - Shoots are rising up from the mustard seeds.
. . .
Day 10 - The mustard is growing tall.
Day 11 - All the shoots are coming up.
Day 12 - The shoots are about one-half inch tall.