Parsley will often bolt when it's transplanted. It's the way it has of protesting! Most plants with a long tap root strongly object to moving house. And if it's been kept at the nursery for a long time, they can actually use growth retardant chemicals to prevent it from growing. Once you get such plants home, and you stop using the retardants and plant them out, the parsley catches up with itself quite quickly and will bolt to seed almost immediately. So, yes, it can happen regardless of the weather you describe (which is about our standard autumn conditions).

I HAVE to share my cilantro growing experience from last year. Last year was the first time I grew cilantro and I planted seedlings in June when it was getting pretty warm. I broke almost all the rules, mostly unknowingly, and it still worked very well. 1) Split each seed into two halves and sowed four halves 1/4 inch deep, equidistant from each other in 2.5 oz cups, about 2 inches across and 2 inches deep. 2) germinated on heat mat. Took almost two weeks to germinate even on heat mat. Most germinated. 3)As soon as I saw any germination in a cup, removed it from heat mat and placed in enclosed porch where they got morning sun. 4)when all the seedlings had at least one set of true leaves planted outside, about mid June. 5) The site was pretty shady, only 3 or 4 hours of sun. The soil was rich, soft and fluffy. Inverted the ball of soil out of the cup, nudged into the soft soil, mulched and watered. ALL the little seedlings grew into big stocky plants! I crammed what turned out to be 24 to 30 plants in a 2 feet by 3 feet rectangle, or smaller. In spite of the little sunlight and so many plants in such a small space the cilantro grew upright, vigorously and had fantastic flavor. And here is the kicker. I harvested leaves by holding a bunch and cutting straight across about 1 or 2 inches from the ground. For most part I did not cut all the leaves off a single plant but a bunch here and there from my dense clump. By the next morning I could see new growth at the cut surface. I cannot emphasize just how much cilantro I cut and harvested from this clump for myself and my friends. And I was harvesting till a little before Christmas until iit suddenly got too cold and I did not want to trek outside anymore. The plants were still growing back in Nov. Not a single plant bolted till mid November and then only a total of three plants flowered. The flavor changed late in the season. Dont know if this was because of the season changing or the plants getting spent. Still pretty full of flavor. I did water well and fed them with fish emulsion + kelp extract a couple of times. So, I germinated inside on a heat mat, transplanted outside in hottish weather, grew in mostly shade, harvested over and over and got cilantro into December from a planting from June and almost no bolting. I attribute all the good things to the variety I grew, Calypso. I bought three varieties, Calypso, Santo and Cruiser, just picked them out of a hat. I could not get a single seed to germinate from Santo or Cruiser so Calypso grew by default. That was one of the luckiest breaks. I am reading the description of Calypso carefully now and it does say very slow to bolt, can be cut again and again and makes big plants. The Calypso was from Park Seed. This year I will plant out earlier. @floral_uk z.8/9 SW UK my last frost date being April 25, I will try beginning of April? @kitasei2: Please give Calypso a try. I think it will work for you. You will get big bunches of cilantro. Same as you, last year the flat leaf parsley I tried germinated in a few days, a blink of an eye. I soaked the seeds overnight and germinated on a heat mat too. I planted them out so late they did not get very big though. Maybe they wont come back this year.

Parsley stems don't go all the way into the ground. They fan out at the base. I have three large curly plants in a large container, and three of the perhaps twenty stems on this one plant have flat leaves. I know of reversion mainly from variegation on plants, which is unexpected color patterns on the leaves. But this is different.

I'm surprised my parsley DIDN"T overwinter for me lol! It usually does, and I love it. It's nice to have those early sprigs before the newly sown stuff grows. This was a bad winter all around for me (although frankly I think I lost more stuff due to the bad spring, not the winter!) but I was disappointed not to have the parsley. I know I've told this story before but I like it so I'm telling it again lol. I used to work on an organic farm, and i am a big champion of organic growing and things having their place in the world. I used to love that when we harvested the parsley, we harvested around the swallowtail caterpillars. We grew extra parsley and if we saw a caterpillar, we would just let it be and cut around it. I just always thought it was such a small, everyday gesture that showed our inter-reliance. It always made me smile, even in the pouring rain or the extreme heat. :) Dee