I am looking for a science-fiction short story, I just remember the synopsis, partly. It's a time travel story, where the main character, a boy at the beginning of the story and an adult at the end keeps returning to a strange garden which is used to launch rockets ? Or something else scientific related. And for some reasons, I can't remember, this garden is flowing with tubes that create some time shifts, essential to the scientific activity. It's strictliy forbidden to come across them but for some reason some day he will, and since that day he will meet a stranger that tries to communicate with him but somehow eludes him. And, big spoiler coming, it happens that this stranger is himself at a different times.
I read it as a part of a compilation of short stories, but I really cannot find neither the title nor the author.
Any hint much welcome, as always.