I want to try growing parsnips in plastic drainpipe. I have a length available but would like to know into what lengths the pipe should be cut. I'm not looking to grow show parsnips, just reasonable ones for the pot. I'll also be sowing seeds into loo rolls and paper rolls for the garden, so this will be more of an experiment. Also, should I use garden compost or normal potting compost for the drainpipe.
Tricia