Watermelon's smell takes me back to childhood, under the plum tree eating watermelon. We sat beside a water faucet, on a small, slatted-wood platform hugging the ground, presumably to keep people from getting muddy when the water splashed onto the ground.
Another smell memory is of my grandmother's hyacinths growing along the side of the garage (on the coalbin side). Those flowers grew next to my sandbox, installed there by my daddy when we moved into Grandma's house after she died. Smelling a hyacinth transports me back to the sandbox, and I can still feel the gritty sand sticking to my legs. When the sand was damp, my brother and I would pack it around our feet and then carefully slide our feet out to leave mounded sand houses, ready for occupancy.
(Response to Goldendaze-Ginnie's post: "The Power of Smell - My First Memory.")