just watch :) drag the "max depth" slider to change how far down the rabbit hole the tree drawing algorithm goes. be really careful though, it makes the lag get really insane. less depth = less lag. don't turn it all the way to 12 unless you want your computer to explode :) (also it doesn't look very nice at 12, hehe) OH and if it still lags, try pressing "see inside". for some reason that fixes it sometimes.
new feature - drag the "mode" slider to the right and manually control the parameters ! have fun designing your own tree & tell me what the coolest looking tree is in the comments :)