Learning about the best parsnip planting times

My parsnips (“Harris model”) said on the package I could do either spring or fall planting. While researching whether this was true for Oklahoma, I came across a useful post on an Oklahoma gardening forum (expand the featured answer by “macmex” who is located north and east of us, in Talehquah in northeastern Oklahoma) It sounds like you CAN plant them in fall, but as a biennial, they may flower (“bolt”) in the spring before the roots are big enough to be useful. So, we’ll see what happens with my fall-planted ones, but I have just put out a row of them today and I will put out another row each week until the third week of February and see what happens to those.

I also read everywhere about parsnip seeds that they do not keep well. Mine are going on two years old now so I put a lot out to make up for potentially poor germination rates.