The bug
The hitbox of the double plants takes up the entire block they occupy despite not being visually larger than fern or simple tallgrass which occupy only about 80%. This is particularly noticeable with sunflowers
Notably, tall seagrass is not affected by this, and uses a more reasonable hitbox - see MC-128237.
Related issues
is duplicated by
relates to
Attachments
Comments


Confirmed.
Still a concern in 1.7.4/5 and 14w08a
Confirmed for 14w10c
Confirmed for 14w18b.
Confirmed for 14w20b.
Still in 14w21b...
Confirmed for 14w25a and b.
still in 15w45a
Confirmed for 1.10.2 & 16w43a
Can confirm for MC 1.12.1.
Confirmed for 17w48a
Affects 18w21a.
And (although unrelated in its effects - mainly stuff connecting/placed on sides of) the actual bounding box size reduction would be consistent with the resolution of MC-128237 which was for tall seagrass.
Edit:
To be consistent since nearly all plants would no longer exhibit a full hitbox, perhaps we should add all crops to the list?
Also, the sea kelp bounding box takes up the full block, and to be consistent with sugar cane (the closest plant that is land-based) the bounding box should also be reduced to the size of sugar cane and other plants.

Confirmed for 18w22c

Confirmed for 1.13-pre1

Confirmed for 1.13-pre2

Confirmed for 1.13-pre3

Confirmed for 1.13-pre5
Confirmed for 1.13.1.
Confirmed for 1.13.2-pre2.

Affects 18w47b

Affects 18w48a

Affects 18w48b, can I request ownership of the ticket?

Affects 18w49a
Changed the reporter to @unknown.
Affects 1.14.1
This shouldn't have been marked Works As Intended, especially for the sunflowers. The hitbox size is ridiculously oversized, and it negatively interferes with gameplay. As it stands, sunflower hitboxes are a relic of Old Minecraft, and don't fit in with modern times.
Although this issue was marked as intended to maintain consistency with other double-tall plants, this comes at a cost. The hitbox is confusing and annoying to players, which prevents them from effectively breaking and placing blocks near sunflowers. This cost is not worth it in the name of consistency, since consistency comes with no benefits to the player.
Additionally, contrast the sunflower hitbox with the more modern additions to Minecraft, like the tightly fit lectern hitbox. Or recall the update when hoppers and anvils were updated with an exact-fit hitbox, greatly improving their usage. It becomes clear that sunflower hitboxes do not work as intended, and are in dire need of an update.
This is useful. If the hitbox is smaller rays wors fern farm doesn't work.