You can sow marigold seeds in Pennsylvania in the spring, as soon as the ground is warm and all danger of frost is past, according to Penn State University. The state's average last frost date ranges from April 14 to June 7. If you'd like flowers earlier, plant the seeds indoors in early spring.
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Aileen Clarkson has been an award-winning editor and reporter for more than 20 years, earning three awards from the Society of Professional Journalists. She has worked for several newspapers, including "The Washington Post" and "The Charlotte Observer." Clarkson earned a Bachelor of Arts in journalism from the University of Florida.