I planted 4 o'clock seeds last year for the first time (in a pot) and had flowers blooming in late August, Sept. I didn't know they produced tubers until I was cleaning out my pots for winter storage. I did some reading up on 4 o'clocks and saved the tubers in a paper bag with some sand and stored them on a shelf in a dark closet. I'm in zone 5a (feels more like zone 4a) and our growing season is short, too. I definitely want to plant them out this year. Is late May a safe time?