cant clean up weeds galaxy s2 android

I have aamsung galaxy s2 android . I cant clean weeds up from the bottom left of the screen. I cant drag my people that far down. How can i get this last weed. Please help me. I wont be buying the full game until i can get this answer

Your little family can purchase a weed bomb in the Varied Items section of the store that will remove all weeds from the yard.