The bug

When a non-op player destroys a double plant within the spawn-protection area set in the server.properties file, the client of that player fails to place again both blocks and the correct type of the double plant which has been destroyed (the client always shows the texture of a peony, see MC-53439). This causes a kind of weird looking graphical glitch.

How to reproduce

1. Set up a Minecraft server. (the server jar for Minecraft version 1.12.1 can be downloaded here)
2. Set the spawn-protection field in the server.properties file to something high. (16 by default)
3. Make sure that you're not opped, but there has to be at least one opped player in ops.json. This is to make sure that spawn protection is active.
4. Join the server, find a double plant, and try to destroy it.