You need an angle, an approach. Well, maybe not always. Writing about previous places, often I've just found it enough to express an evocative image. Setting myself the task of writing about autumn makes me even more sympathetic to children faced with this requirement. I need to think how I feel about it - and that's a task in itself.
The best I can come up with is - mixed feelings. And continuing that thought, perhaps that does link quite naturally with some of the things I've noticed, such as the flowers of summer next to the leafless branches, or the trees with green leaves on one side and brown on the other. Ok, that gives me a starting point.