JJ216, I hate to give you one of those it depends answers but it does.Where i am located the rye generally peters out about april 1-15.We frequently experience late frosts up to april 15th.The crabgrass seed seems to be very soil temperature sensitive and no i don't know the needed temp.If it stays pretty warm and the right rains it usually is ready to graze in 30 to 45 days.Kind of a poor answer but the best i can do.The seed does much better if you can run a roller over the field after scattering the seed or after discing if you have an established seed bank in the soil.As the previous gentlemen pointed out it does not do good on clay soils, and Mr Dalrymple pointed that out to me when i asked about putting it on black gumbo.On a side note one of the old sandy land peanut farmers in our county about had a stroke when i told him i was going to plant crabgrass,he said he had fought it his whole life.