Most of maples species' seeds are starting to ripen right now I think. As a rule of thumb though, if part of the samara has started to turn brown while the central part of the seed is still green or colored, it is ripe and safe to pick. You can also wait until the entire samara has turned brown before picking it as they will usually stay on until the leaves start to drop in fall. But if they are brown (and therefore dried) you might try stratifying them to help increase your yields. They dont germinate very easily and this could increase yeild from 25 percent to over 75 percent. If there is some green on the samara you may get better yeilds without stratifying, but still not in that 75% range I dont think.

thanks for the info.!

i will try all your suggestions and experiment a little.

the samara has started to turn brown , yet the the seeds are green at this point.