How do you get these impossible Pokeballs?

Question

I found some Pokeballs by the Cave of Being, but it seems impossible to get. How do you get them?

Comments

What are they called?

Answer 1

You need to wait until your game changes seasons to Autumn. Then the leaves will cover up the ditches and you can walk on top of the leaves to get the items.

Sometimes you'll fall into the leaves and need to squirm to get out, not unlike the bog in Route 212 (I think?) in Sinnoh.