Then drop in the water, one by one, to see what happens. Use two similar, healthy plants. Ask your child to water one plant and ignore the other for a week or two, keeping both plants in the same place. At the end of that time, ask your child to water the drooping plant. Then talk about what happened and why.
Plants usually perk up with water just as children perk up with good words and smiles from parents.
There are opportunities everywhere for teaching and learning.