Dennis and co have to grow some cress for a homework assignment super-fast, or risk getting a detention... on the day of the Beanotown Comic Convention! Disaster! The menaces concoct a super plant food and borrow some exotic seeds from the Colonel - a keen botanist, naturally - but it works a little too well and soon Dennis and his pals have to deal with an overgrown lawn, and some errant water-cress hybrids with an insatiable appetite.