Pokémon HeartGold weird tree help!

I'm at the Sudowoodo part.
Somebody said something about that you must shake it...What must I do?
(Sorry if this is noobish)BTW, I'm using a Dutch game (patched)

Erhm, it was soaked.

go back to goldenrod,go to the flower shop.Talk with the woman and she'll give you
a squirtle can.Go back to the sudowoodo,use the squirtle can and then kill/capture it.
Try to catch it,because I think it must be the only sudowoodo in the game.EDIT:You're welcome

Replying to #4

Thanks.

Squirtbottle. Get it from the house next to the Gym in Goldenrod