As long as Venusaur is in play, Energy cards attached to your Pokémon can't be removed by your opponent's attacks or Trainer cards. (This doesn't stop the rest of the attack or Trainer card from working normally.) This power never stops working.
Flip a coin. If heads, the Defending Pokémon is now Poisoned. If tails, the Defending Pokémon is now Paralyzed.