Thank you and new question

Thank you to all who replied to my request for shade plants. Now I have a new question.. I just found out that we live in a 5b hardiness area and I am now looking for information on perennial plants that will grow well here. We are right at the border of a 6a hardiness area. I brought a few plants from my previous home (5a area) and somehow some of them just didn't survive over the winter..including a nice and tall coreopsis which flowered from August to about October.. I have started some seeds indoors and they are doing well..I am hoping to be transplanting them in a week or so. I remember when I lived in Toronto (6a Hardiness area) that the garden section of the paper determined that April 20th was the safe day to start gardening outdoors, planting directly outdoors, this correct? And what is the appropriate date for the 5b area?
Thank you all in advance,
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