shule1

You don't necessarily have to let them ripen *that* long, although it might be ideal.

I've taken seeds from a huge, green cucumber taken from a live plant, and they had excellent, fast germination. I think it has more to do with how well-formed the seeds are than how old or ripe the cucumber is (same for tomatoes, despite what people say). Fruits can have early and delayed ripening, but I don't think this necessarily corresponds with when the seeds are ready (although that may be a useful rule of thumb if you don't want to risk having immature seeds). I thought maybe I should go on the safe side and plant lots of the seeds just to make sure I got at least a few plants (but I got loads of plants).

It can be hard to tell if an unripe fruit has mature seeds, though, but for tomatoes at least, I've found that they seem to be fine if the fruit is near its ripening point, even though it's not ripe; so, I don't balk at saving seeds once the fruit has only a small color change on it (and you get fewer seeds with spots on them this way, too). On the other hand, I've had several varieties without mature seeds even with totally ripe fruits; they might have been parthenocarpic, though (it seems they needed further acclimatization to get good seeds, because the ones that lived produced normal seeds after being in the garden longer). As for if it makes a difference in the next generation's mature plant quality and fruit quality when you save seeds earlier than total ripeness, I can't say.