You touch one to three pieces of ammunition and imbue them with a unique toadstool magic, causing them to grow plump green mushrooms around or at the tip of the ammunition.   When a creature is hit with a ranged weapon attack using the ammunition, it takes an extra 1d6 poison damage and must make a Dexterity saving throw. On a failed save, the creature is pushed back a number of feet equal to the damage taken (rounded up to the nearest 5 feet) to a maximum of 15 feet. Whether the attack hits or misses, the spell then ends on that piece of ammunition.   If you cast this spell again, the spell ends on any ammunition still affected by your previous casting.