Hypericum (Rose of Sharon) is a cool temperate plant and normally the seeds would be produced in fall. I would be inclined, especially in view of the very warm summer temps in USA right now, to delay sowing until at least mid- September. Follow the usual precautions: sterile compost etc. BTW the flowers of all Hypericums are yellow, it is only the foliage which, in this case, is purple! Good luck

Rose of Sharon is usually used to refer to Hibiscus syriacus in the US.

Thank you for the help. It is greatly appreciated.

mmstorms - the answer ifraser25 gave you is excellent but unfortunately it refers to the plant known as 'Rose of Sharon' in the UK, ie Hypericum calycinum. The plant you refer to as 'Rose of Sharon' in the US is Hibiscus syriacus, as purpleinopp says, so the info is not necessarily relevant. I have never grown it from seed so cannot help from first hand experience. I grow shrubs vegetatively, ie cuttings etc, to ensure I get an identical plant to the parent. Seed can give variable results. The link might be useful.

Here is a link that might be useful: Hibiscus syriacus from seed

mmstorms - you live in South Dakota--what is your USDA zone? Hibiscus syriacus/rose of Sharon is rated as winter hardy to zone 5 & warmer. I'd hate to have you grow seedlings only to lose them to a cold winter.

South Dakota USDA zone is 5A