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MC-228758

Most saplings cannot grow if there is a block diagonally above it

The bug

Most saplings (acacia, both azaleas, birch, spruce, jungle saplings) cannot grow if there is a block diagonally above it. This does not mangrove propagules (sometimes) or any type of mushroom/fungus. In the case of oak saplings, this prevents small oak trees from generating, but not big oak trees.

The growth is also only (generally) prevented by blocks that have a collision box, but it does affect buttons, light blocks, planks, twisting vines and even flowers for some reason. It does not affect the following blocks (list might be incomplete):

  • Tall grass

  • Glow lichen

  • Logs

  • Vines (sometimes; see MC-193318, affects certain trees)

  • Wood

Linked issues

Attachments

Comments

ampolive

I thought this was only an issue with azaleas and with non-full blocks, but with more experimentation it turns out all saplings (except oak saplings) do this with any (collidable) block. This might very well be a duplicate, but I didn't find anything using the search feature.

Now I recall that this also happens in older versions. If this is an intended feature, it should be the case for oak and spruce saplings as well.

ampolive

The block also does not need to be immediately above the sapling, it could be up to a few (about six) blocks higher than the sapling and still prevent its growth.

ampolive

Attached a test world.

ampolive

I assume this should have the category "World generation" too, like most other tree-generation issues.

user-f2760

It's worth noting that for oak, it does prevent SMALL oak trees from generating, just not big ones. (this is a trick I've been using for a long time when I want big oaks while building).

ampolive

Updated description. Thanks for the info.

Brain81505

Can confirm in 23w03a

Wormbo

Can confirm in 1.21.
Diagonal blocks have been a way to force oak saplings to only grow as "fancy oak", i.e. (usually) large oak trees. I'm reasonably sure this behavior has existed for a long time, and currently a very intentional-looking check in the TreeFeature class. The thing that might not be intentional is that trees that generate with vines or other blocks, that are neither leaves nor logs, don't necessarily ignore those block types.

ampolive

(Unassigned)

Confirmed

Gameplay

Low

Block states

sapling, tree, tree-generation

1.17, 1.17.1 Pre-release 1, 1.17.1 Pre-release 2, 1.17.1 Pre-release 3, 1.17.1 Release Candidate 1, ..., 1.20.1, 1.20.2, 1.21, 1.21.3, 1.21.5

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