Flat Leaf Parsley

 Pick a spot that gets full sun (6+ hours of sunlight) and has well-draining soil that’s rich in organic matter. This herb needs more fertile soil than most herbs. Soil pH should ideally be around 6.0—slightly acidic. Parsley seeds can be started indoors or sown directly in the garden. However, the taproot of parsley plants is delicate, so take extra care if transplanting!

For a head start, plant seeds in individual pots indoors 6 to 8 weeks before the last spring frost date.
Sow seeds outdoors 3 to 4 weeks before the last spring frost, as parsley is a slow starter. 
For the best germination, soil should be around 70ºF, though parsley seeds will germinate in temperatures as low as 50ºF . The germination rate of parsley seeds tends to be low, so consider soaking the seeds overnight before sowing to improve your chance of success.
Sow parsley seeds 1/4 inch deep.

Sow seeds about 6 to 8 inches apart. For larger plants, sow about 8 to 10 inches apart.
Be sure to keep soil moist while seeds germinate. 
It can take 2 to 6 weeks for seedlings to appear. 
Plant radish seeds in the gaps between parsley seeds. The radishes will sprout and grow before the parsley appears, and the radishes will mark the row.
Indoors, you can use a grow light to help seedlings grow. Make sure it remains at least two inches above the leaves at all times.

When the leaf stems have at least three segments, parsley is ready to be harvested.
Cut leaves from the outer stems of the plant whenever you need them. Leave the inner portions of the plant to mature. Ideally, allow 2 to 3 weeks for regrowth between major harvests. 
If you want fresh parsley throughout the winter, replant a parsley plant in a pot and keep it in a sunny window.