Seeds should be allowed to ripen completely on the plant. This is a true statement, I believe, whether the seeds are in pods, capsules, heads, in fruit, etc. Seeds that leave the mother plant of their own accord can be presumed to be ripe. Hopefully, someone will jump in and correct me if that's not an accurate statement.

It varies widely by species and each plant undergoes characteristic changes that lead to maturity that would need to be known to establish the optimum harvest time. Generally, it's best to allow the seed to realize full benefit from being attached to the plant, but some seed bearing organs never detach. Often, wind, animal ingestion, splitting of the pod and subsequent dispersal or other strategies come into play.

When the flow of nutrients, water, and metabolites to and from the seed producing organ stop, there is no further benefit in leaving it attached to the plant. As a general rule, seeds produced in pods generally have mature embryos when the stem is more brown than green. Seeds of fleshy fruits are mature when fruit is ripe. Many flowering plants with compound inflorescence have mature seeds when the back side of the flower and or petals turn brown.

Some seeds (mainly trees) are purposely harvested when immature because if seed coats are allowed to dry and harden, germination time is greatly increased, sometimes for a year or more.

So, your greener seeds may or may not be viable, depending on how mature the embryos are. It is also possible that they will germinate and lack vigor if not sufficiently mature. As Dorie says, it's generally better to allow the seeds to remain on the plant as long as possible, but harvest them before Mother Nature takes up the chore of sowing them herself. ;o)

Al

While we were growing up our Dad had us pick the seeds off our morning glorys every season. We pretty much waited until the pods were somewhat "crunchy". All we had to do was squeeze the pods and maybe give it a very small twist to break the pod and the seeds would just fall down.

By the time we harvested seeds, there were no more green pods.