I tried to propagate Arabian jasmine and hydrangeas but so far, I don't have much luck with either. Here's what I did. I put the cuttings, one in its own pot and covered it with plastic bag. I opened the bag every 7-10 days to check for new growth. The minute I see new growth, I removed the plastic bag and leave the pots in indirect sun areas. I make sure the soil is moist but my cuttings always do not survive at this stage.

What did I do wrong and please advise on how to propagate successful please. Thanks

Without a longer description of the actual symptoms that happened near the end, it is hard to guess. Too much water moisture? I would make sure that cuttings are not in too soggy conditions, water does not collect at the bottom of the pot and the drainage holes are working. Aim for moist, not soggy or dry. I hope you are not trying to use oakleaf cuttings because oakleaf hydrangeas are very difficult to propagate via softwood cuttings. I happened to get lucky once but for those, I would use ground layering or grow from seed (the seedlings would not be identical to the mother plant).