I wouldn't worry, if it was my relative. If the gardener doesn't seen upset I would assume he - his soul or whatever - is not there and what was being seen was some sort of earth memory of someone who'd done the same thing every day for many years. Which begs the question of why doesn't everyone who does something repetitively leave such an imprint - well, I don't know. There is no data to speculate on so I don't often contribute to ghost discussions. But I am convinced that people do see ghosts, and they are not individual hallucinations. But whether there really is something objective to see or whether they are some sort of group mind thing - as, I say, no data.