Encourage your child or grandchild to develop an interest in gardening by having them grow a plant from a seed. Place 3 toothpicks evenly around an avocado seed and suspend it in a jar of water so that the bottom is always covered in water. The seedling which will eventually emerge can be transplanted into a pot when it is about 6 cm tall. The same can be done with a sweet potato – be sure that there are several eyes above the toothpicks.