They proc keystones and other Runes
They proc item effects 
They count as spells being blocked by 
I just find it odd how tagging someone with a Q-plant will proc all of these things but it wont work with Manaflow Band.
The entire team1 votesIt’s because Manaflow procs from hitting an enemy champ with a spell. Zyra’s plants are separate, as they are minions, not spells.
LeoiJw1 votesBut they proc spell effects is what I'm saying, which means they're counted as spells, which means Manaflow SHOULD proc.
Same should go for any pet I would say.
Illabethe1 votesspell effect =/= spell. Sometimes the actual context matters.
Like..... with On hit and On attack effects. On attack effects are more limited in application than on hit effects.
LeoiJw1 votesThat makes no sense and just seems like lazy coding especially considering the fact that the only thing that plants and other pet-minions can't proc is Manaflow.
Illabethe1 votesIt allows them to add more levels of governance to item/rune interactions that help balance them on one kit versus another. The fact they generally allow Ezreal's Q to be a Spell, an On hit effect, and used to count as an attack is the sole aberration in this balance, and is why they eventually removed the on attack criteria (it was double proccing certain runes/Muramana)
If all on hit effects and on attack effects were the same thing, Illaoi's W would proc certain effects three times. VERY hard to balance.
