Do Summoned creatures trigger "on death" effects?

Question

Taking Leshies as an example, they can be summoned with the Summon Plant or Fungus spell. They also have the Verdant Burst ability (abbreviated):

When a leaf leshy dies, a burst of primal energy explodes from its body

The entry is slightly different for each form of Leshy, but they all give an instantaneous healing effect to nearby plant creatures, and most cause the area to become difficult terrain for 24 hours or permanently.

However, they also gain the Summoned trait, which states:

They are automatically banished if reduced to 0 Hit Points or if the spell that called them ends.

Which of these triggers first? What if the leshy is killed by massive damage? Is there a distinction between the instantaneous healing and the lingering difficult terrain (if the healing occurs, is the terrain then banished with the Leshy)?

Answer 1

Most Likely Not

As per the rule you quoted, they are automatically banished if they reach 0 hit points. Banishment is different than death; since the Summoned trait is more specific than the general death rules, banishment takes precedence. From the text of the Banishment spell, banishing is described as:

You send the target back to its home plane.

It's very important to note that 0 hit points does not mean dead. The death and dying rules have this important statement (emphasis mine):

When most creatures reach 0 Hit Points, they die and are removed from play...

Combining these two, it seems that banishment is intended to replace the effect of dying for summoned creatures. That being said, this isn't as clear as it could be, but this seems the most logical and rules oriented (rules as intended and written) approach until errata gets released.