Most veggies will grow immediately from this years seed... just depends how long the season is... whether we get a crop.
Last year... I replanted my glass gem corn and got 2 generations the same year.
I also replant my beans as soon as they are mature... for another generation.
Apparently a common practice with growouts for seed companies who have access to land in Mexico... helps to create daylight neutral varieties.
There are some seeds that I've planted that wait until next year to come up... like sunflower...
Might make an interesting experiment.