In Bean Valley, you find a Smilax that gets watered by a Shy Away until it turns into Megasmilax.

Defeat Megasmilax

The battle starts with just one Smilax, and when you defeat it, two Smilax appear, and after you defeat those, three Smilax appear. This is followed by two Smilax and a Megasmilax.

Megasmilax can cast Petal Blizzard, which turns characters into mushrooms, and S'crow Dust, which turns characters into scarecrows (unless they're wearing the Trueform Pin or similar). It can cast Flame Wall, which does moderate damage to the party.

Afterward

After the battle, the Shy Away runs away. Read the note that it drops, and you get a Seed. Then go down the pipe that Megasmilax was on. Hit the floating brick to make a beanstalk appear. Hit the brick to climb up it.

In the cloudy area, read the note on the vine, then climb up (or jump away from the vine to get off of it). At the top of the vine, jump while holding the run button to jump onto the yellow vine. Jump from there to the vine on the right, and when you climb up, you see a Frog Coin. You can optionally try to jump to the Frog Coin to get it. Then climb up the rightmost vine to reach the next area.

You can go up the rightmost vine to find a chest that contains a Flower. Then you can try to jump from there to the middle vine, but if you don't make it, you can climb up the rightmost vine and go from there to the middle vine. At the top of the middle vine, there is a vine on the left and a vine on the right.

Optional: Left Vine

From here, you can optionally jump to the leftmost vine (if not, skip to the next section), then climb to the top of the leftmost vine to reach the next area. Climb up the middle vine, then go up the vine on the right, and try to get the coins and Frog Coin if you wish. Then jump onto the middle vine. Stand on top of the middle vine, in the center, and jump to reveal a floating platform. Jump back onto the vine on the right, then jump from there onto the platform that you revealed. Then you can jump to the leftmost vine. Climb to the top to reach a new area where you find a Frog Coin and a Rare Scarf. Then jump down the eastern hole in the cloud, open the chests to get two Flowers, then fall down the hole to end up in Nimbus Land.

Right Vine

If you went up the right vine instead, you have a straightforward path up the vines and can try to get five coins. At the top, you reach Nimbus Land.