It's true! Waaaaaaaaaah. It's also the last challenge Specklet has to complete, so it's not like I'm the only one who can't work it out :)

It eludes me as well. But here's a very cute and related video.

Wait, do you mean at the end of the Adventure?

Julen: nope, not the end. There's a series of achievements you can do (eg, a pool level using no pool plants, freezing 20 zombies at the same time, having 10 double sunflowers on the screen at the same time, etc), and the one we're both stuck on the Pyromaniac challenge. Everything we've tried doesn't win the challenge.

This is all I could find: To get pyro just use peppers, potato mines, cherry bombs and exploding shrooms. I didn't use garlic or nuts and it worked. Garlic and nuts seemed to prevent the achievement from registering. I also didn't use a rake or let a lawnmower go off.

Others said "no nuts". I have no idea what that means, but hopefully it helps.

Hunh. I thought I had completed all the challenges, but this isn't ringing a bell for me.

...

Oh I see the problem now - I don't have the right edition so no achievements for me. Well crud. I wish I could add on achievements instead of having to rebuy.