Any time now as long as you harden it off properly first. Mine overwinter outside, so they are fairly hardy.

thanks volunteer

I leave mine out all year too - if you had it last year, Sunshine, keep a close eye on "weed" seedlings popping up - verbena bonariensis seeds itself and pops up all over the place, so don't hoe out any seedlings without checking first.

thanks bamboo

Seedlings have dark green serrated leaves with a purple tinge to the stems. You soon get to recognise them!

Mine grew in between the paving too ... persistent little seedlings !