I respect Flannery's work but I find it hard to enjoy much of it. She never seems to pity anyone she tortures. The only story of hers I truly love, rather than merely respect, is "Parker's Back," and partially it is because I detect in it a whisper of pity for Parker. This is also one of the last stories Flannery wrote before lupus claimed her, and that makes me wonder if she might have written more stories I could love if she had lived longer.
An important note is that while one tree is the Cross, lots of trees together in a Flannery O'Connor story always mean that something really bad is about to happen. (Edmund Spenser had a similar thing with trees: whenever you see them in The Fairie Queene someone's in trouble.) And actual crosses pop up where they have no business being; I personally find it difficult to picture someone with a "cross-shaped face."
I would say more but I have gotten my annual sore throat heralding the descent of the year and I need to go to bed.