Plants don't grow when there is block above them

I am also having the same problem. The pumpkins and Melons on the top row are growing but the ones on the bottom are not which are underneath the row of dirt blocks. This is in 1.13

I'm pretty sure this behavior is not new to 1.13, at least for blocks directly above it. I remember encountering it in prior versions. You always needed at least 1 air space.

Perhaps dirt was previously special-cased though and worked in the past but doesn't now? That'd be the only explanation for a sudden creation of new reports for this when none seem to have been made in the past (that I could find).

I also remember needing at least one block of air above crops. Not sure why this is being reported now.

This wasn't the case at least for melons and pumpkins, they would grow perfectly fine in one block high spaces in 1.12.2. I have a stackable pumpkin/melon farm (Xisumavoid's design) that stopped working after updating to 1.13.

Edit: I just did some more research and you're right, crops always needed a block of air or a transparent block above to be able to grow.

What apparently changed is some property of the farmland block (transparency?). With a farmland block above a pumpkin stem, pumpkins could still grow in 1.12. In 1.13, this doesn't work anymore. Other transparent blocks above the stem (glass, pistons) will not prevent pumpkins from growing even in 1.13.

This might be related to the change that caused pistons to no longer be transparent, which was reverted in the 1.13 prereleases. (MC-130858)

The farmland change is definitely much more plausible. And yeah, it's definitely some kind of full block thing (I remember actually having a weird case where double slabs would let plants grow, but gold blocks wouldn't; however, this was ages ago).

I can't see any obvious change about the block itself, though, looking at the code. Neither stems nor farmland have changed.

The condition seems to be the light level of the block above being >= 9; maybe something with the light engine is making farmland different? Unfortunately I don't know the light engine at all so I can't diagnose that.

EDIT: Actually... that makes little sense; farmland has been considered light level 0 for a long time (MC-46667). So that doesn't make any sense... I see MC-2399 which was fixed, but that ticket only mentions rendering, nothing with the actual behavior in F3. (also, note that that bug may have been fixed earlier than 18w05a; 18w05a was the first time it was noticed)

I just wanted to confirm that I am seeing this issue too. I have a pumkin/melon farm from 1.12.2 and after upgrading to 1.13 the pumpkins/melons aren't growing anymore and there are farmland blocks directly above the stems (stacking style farm).  After some testing it seems that the crops grow if there is a transparent block such as glass or air above the stem but not if there is a partially transparent block such as farmland or slab. It seems to only matter what the first block directly above the stem is, so this isn't a sky access change.

I don't remember seeing this being mentioned as an intended change and so I'd personally class it as a bug. I hope that helps.

not fixed for melon/pumpkin stems

Sweet berries do not grow with certain blocks (seemingly those opaque to light) above them