I am starting seeds, mainly tomatoes, peppers, eggplant, cucumbers, and melons, but I don't know when to start and transplant them. I am in USDA zone 6a.
Fayette County Pennsylvania
Thanks for your question. You need to know the average last frost date for your area. Here is a link for the Fayette County Extension Office to get that date:
Penn State offers a great book on vegetable gardening that explains when to start seeds and how to grow many vegetables. Here is a link to the online version:
Vegetable Gardening: Recommendations for Home Gardeners in Pennsylvania