Have not grown the parsley root.
Stop reading now if you don't want to follow a bunny trail regarding volunteerism in the garden.
I grow parsley every year. Accidentally grew curley leaf last season, and was very pleased with it. I have always chosen the Italian flat leaf in the past. Parsley is one of those crops that you can have forever if you let it go to seed. It is a biannual, so you have to plan for that. If you keep a neat garden, and till it completely every spring, you are not going to want to keep a plant that gets quite exuberant as it goes through it's second season. But, for me, that's a non issue. I have volunteers all over the place: garlic is the primary offender. Also Egyptian onions. Then there's the dill. Oh my! I vow to try to control that, but never succeed. And the raspberries which have now spread into the asparagus bed. And, the lettuce! Love that volunteer lettuce. And the calendula, and nasturtiums, and sunflowers! Last year, I let an over wintered chard plant go to seed, and also harvested a huge crop of kale seed.