It's been ages since I grew them in containers, but I remember them doing well. I'm in z5 like you, but many years ago I planted some near the foundation, under a large window that has an overhang. As a result of all those factors, it's a zone warmer in that spot and my 4 o'clocks come back for me on their own every year. They've now started to self-sow like crazy too. :)

My #1 advice: remember that the flowers don't open until evening or on dark/overcast days, and will only stay open until mid morning at best, so place it where you will see and enjoy the flowers at those times.

In my area they are very invasive, & terribly hard to get rid of. For that reason I would only grow them in large pots.

I am fond of a white variety called mirabilis longiflora but will only grow the m.jalapa if I can get hold of single colours - I really don't care for the mixed selections, especially the broken flowers. Sometimes possible to get seeds of just the deep pink. It has been a while since I grew them but I recall the fat seeds germinating quite rapidly in heat (I didn't use a propagator but did do a late April sowing). Very quick to grow once the true leaves appeared. I had them in the open ground where they quickly formed a substantial bush but I didn't keep them because of space issues.

I've had M. jalapa returning here in the border for the past few years - sometimes, apparently from overwintered rootstock in KY zone 7a.

M. longiflora is a cool plant with long tubular white flowers which are fragrant at night. It also forms a woody rootstock and is surprisingly hardy, at least into zone 6.