Once per turn, during the Battle Step or Damage Step of this card's attack, when your opponent activates a card or effect, you can select 1 "Naturia" monster in your Graveyard. Special Summon that monster from the Graveyard.
Summon Naturia Pumpkin when your opponent has a monster in the field, its effect will activate which lets you summon a Naturia monster from your hand. You can then Special Summon Naturia Stag Beetle since it has a pretty good attack when special summoned and it has a good effect. Due to the activation of Naturia Pumpkin, Naturia Hydrangea's effect activates which is you can Special Summon it from your hand. This makes you have 3 monsters in the field in 1 turn.