Fertile soil spams tall grass when it is placed on it.
Steps to reproduce:
Place fertile soil.
Grab grass from decoration tab.
Place decorative grass on fertile soil.

Grass grows to talk grass version. After growing to the tall version, it will start spamming an item called
minecraft:double_plant

After further testing this happens with all 2high plants from the decoration tab.

Huh, maybe ill do that

Thank you for the idea. Its not spamming now :)

Yes, i know, but thanks. I even used this to my advantage, cause i dont know how to fix it

How did you use it? I must have missed that part in the book.

Do you check the block above the soil before a growth tick is applied? The list of 2 tall plants has only 7 items. Any chance that blacklisting these items as part of an if statement would work?