Oh, if you have extra seeds/soil, you can plant your 8, then pull up the first and replant for cross chance on all. That final krakka of yours has a chance of trying to cross to the broombrush or the mandrake.. and cross is decided at the time of planting, so something showing krakka->mandrake on the gardening website will not work if you plant the mandrake first.

It is an interesting idea though.. so best of luck!