Parsley (cool-season biennial herb) is classed semi hardy in the cited extension guidance. The timing rules below are relative to your local freeze dates — enter a location to turn them into calendar dates.
The rules this site applies
Method
Frost-relative window
Rule & reconciliation
Start seeds indoors
13–11 weeks before the median last spring freeze
Wisconsin: start seeds indoors 8–10 weeks before the last frost (UNH: 9–10 weeks from seed to transplant). Parsley germinates slowly.
Transplant outdoors
3–1 weeks before the median last spring freeze
UNH: set out 2–3 weeks before the last frost; Oklahoma State plants 3–4 weeks before. The later UNH range is used.
Direct-sow outdoors
4–2 weeks before the median last spring freeze
Oklahoma State Table 1: plant parsley three to four weeks before the last spring frost.
Seed germination soil temperature: optimum 75°F (optimum range 50–85°F); minimum 40°F, maximum 90°F. Purdue HO-186-W Table 3. Cold soil below the minimum rots seed — a reason windows and soil readings both matter.
Variety assumption: Leaf harvest begins about 70–90 days from seed.