You can get past the giant plant by visiting the fairy queen, she's in the same area as where the plant is but the route is a bit hidden. Just move your character near the northern area where the plant is(it can be found with your senses high enough or you can walk towards it you should run into it). You will need a bottle, fairy dust, and cheese. You can get the bottles in the Lower Ark area, the fairy dust from the fairies that fly around in the park, you also need a machine to make the cheese which is found in the upper Ark area. It is recommended to go to the milk farm and starts Bell's route to set that up.