The trick with the Apprentice in longer grass is full throttle and full up elevator take offs directly into the wind. You still need to find a bare patch of about a metre so it can get going. The prop wash over the elevator helps keep the tail down and the plane will break ground in less than 5 m.

It is a bit hairy when you first start, because you risk a prop strike at WOT, but works so long as you start with a metre or two of bare ground. I used to use a large piece of carpet (6' X 6') at one location.