I have heavy clay soil and have grown gladiator for the past few years. They grew massively long and I had such trouble trying to prise them out. I tried guernsey this year, half as long, omg they have grown three times as wide and are bolting so out they come. This time I had to use a crowbar and the parsnips are like wood. So no more home grown parsnips for me, I am getting too old to be prising them out. I ended up with backache and value for effort, they are so not worth it for me. My plot isn`t that big so whatever I grow has to be worth while and parsnips are joining my blacklist