Try to use the mutandis, in 0.5.2 I used it on grass and i got myself a birch sapling I think, and it did drop the saps 100% sure, rewatch my vids if you want to see it.
https://www.youtube.com/channel/UCSangSi00eRUmOV2DmoWqNA
https://www.youtube.com/channel/UCSangSi00eRUmOV2DmoWqNA