There is a great deal of variety in plants. I can only say what usually happens.

Usually in my gardens, parsley is robust and vigorous the first year. If and when it comes back the second year, it is rather meager and quickly bolts (goes to seed). I have also had stressed plants bolt the first year. And even other plants like the one in the garden now that grew from seed I planted in April 2008, I cut it to the ground at the end of the 2008 growing season. April 2009 there it is again. I cut it to the ground again and rototill the garden. It survived all and sprouted again and is still going strong.

In short, enjoy the parsley while you can and do not expect it to return with any vigor. If it does, enjoy it and be happy but have seed ready to plant new plants.

FataMorgana

Frankly, I don't even really like parsley, though I've decided to give it another go, and see if I can change my mind. These are just volunteers that wandered in from my neighbor's yard, and being who I am, I certainly can't turn down a free plant...or in this case, several dozen free plants.

They wandered into my vegetable garden, which at the moment I reserve for annuals. I potted up some and gave it to my mother, who put them into her garden, and she reports that they're doing well. I moved some across the yard into my herb bed, and those are doing fine. For good measure, I potted up a few more and brought them inside for the Winter...I don't have high hopes for this last set, but hey, what have I got to lose? Meanwhile, there are still plenty of plants left at the edge of the vegetable bed, which could very well still be there in the Spring.

So really, I don't have anything to lose if none of these make it. They were volunteers, and I have just dozens of them now residing in 4 different locations, and I don't even really like the stuff! If none of these make it (seems unlikely, frankly), I doubt I'd bother to plant more seeds. After all, more will probably wander in from the neighbor's yard next year or the year after!

I'm just wondering if I'll see them bear seeds (and prolifically reseed themselves, it would appear) every two years, or every year, based on the calendar.

It's a rule of gardening that the plants you don't particularly like will do especially well, and the ones you treasure just WON'T do it for you!

My experience with parsley is similar to that of Fatamorgana's. Self-seeded parsley seems to be a thing unto itself. It can pop up where and when least expected (or wanted), and it will go to seed when it feels like it, but especially when stressed (unseasonable hot weather, or not enough water, for example).

Plants do not recognise a calender, so don't expect them to abide by it.

You can always weed out the unwanted seedlings.

It's a rule of gardening that the plants you don't particularly like will do especially well, and the ones you treasure just WON'T do it for you!

Truer words were never spoken!

I half joke and am half serious when folks ask how to get rid of mint and I tell them to just want it for tea or something else they would harvest it for. It will make a full-retreat once you want it for something!

And self-seeded plants, there are none so vigorous in the rest of your garden as those. All the calendula grown in my garden this year was self-sown. I grow them in the vegetable bed to encourage pollinator visits and this year's self sown ones were very large and productive plants. They even crowded out the carrots and radishes where they came up. And here in December they are still producing blooms and while we had a very mild November, December-blooms in Western NY State is really something!

FataMorgana

Leira:
Maybe if you mix your parsley with something you might find you like it more. It is a catalyst herb in that it enhances the flavors of whatever it is mixed with. That is a large reason why it is considered so important as a culinary herb. I could make great pesto without it. It has been my experience that home-grown parsley that is well cared for and not stressed is much sweeter in flavor that any store bought I have ever had. Anyway good luck with your growing experiment and
Happy cooking and growing David

You know, when I didn't ever cook with parsley and didn't really know what to do with it I didn't like it either. Now, it's practically a staple veggie in our kitchen. A great way to get green leafy vegetable servings every day without having to have salads and spinach or collard greens all the time.
I buy tons of it, waiting for my fall planted to get big enough, this is the first year I've planted it. Try some recipes that call for it in soups or sauces. I like it mixed with fresh basil in a pesto or spaghetti sauce. It's great to add a cup or two chopped to just about any soup, scrambled eggs, meats, potatoes. I can't think of hardly anything it wouldn't be good in except oatmeal, LOL!

I just now reread a part of my post that reads wrong!!
I could"not" make good pesto without parsley as opposed to could.

Tracy you are sooo right on!

It is a challenge getting parsley through our southern summers so fall to spring is when I have the most to use.
Happy Growing David

It is a matter of developing taste for parsley like anything else. I, personally grew up using parsley both fresh (in sandwiches, salads) and cookings. I pick some often from my garden and eat it as it is. It is similar to celery, that also I like. In cooking, it enhance the flavor of red meat and chicken. As fresh, it is the best breath freshner after having galics.

Today, the shortest day in the NH, I harvested my parsley. I had a bagful of it. I chopped and put them in several small feezer bags.It was a rewarding experience.

After harvest, I mulched the patch lightly with leaves, such that young parsleys barely seen. Knowing that this past season's parsleys will be finished next summer, I have already sown new seeds in the patch to replace the old one.