In the past there has been a lot of talk on this forum as to when to tell when clematis seed are ripe and if they are fertilized. I decided to take a couple of pictures of my clematis seed to show the variation in size of various mature seeds. There is indeed a lot of variation in size depending on the cultivars and here is one shot of just a few clematis seeds to prove the point. Sorry I couldn't zoom in closer for more detail but I have an older digital camera that doesn't have a macro function.

{{gwi:587925}}

From left to right in the photo are seeds of crispa, viorna, glaucophylla, integrifolia Hakuree, and Julia Correvon.

Another point of contention is when the seeds are mature and ready for picking. My position is that seeds do not have to be brown to be ready for picking. Once the seed reaches maturity and has stopped drawing nutrients from the seedhead, the tissue that connects the seed to the seedhead begins to deteriorate. Some time after that happens, the seed begins to go through various color changes-from obviously green, to light green, to a sandy tan color, and then through various shades of brown. If the seed has feathery plumes, they begin fluffing out at this stage. The seed is theoretically ready for picking as soon as the tissue connecting it begins to deteriorate. Since you can't really tell when this deterioration actually begins, I use the color of the seed and if it will easily come off the seedhead as my guides to know when to pick. Following are some pictures from my garden.

The picture below is one showing a seedhead of Roguchi that shows two seeds at 7 and 8 o'clock that are fertilized and still very much green. I might pick them if I thought frost would prevent them from maturing.

{{gwi:587926}}

Below is a picture of the seedheads on my glaucophylla plant. In the picture, the feathery tails are expanding, the seeds are light tan in color, and they come readily off with minimal use of my hand. Definitely ready for picking.

{{gwi:587930}}

Below is a picture of one of two of my pitcheri plants. In this plant, almost all the seeds are fertile and plump but still very much green. I would prefer to wait longer to harvest these but would pick now if frost threatened.

{{gwi:587929}}

Below is a picture of another of my pitcheri plant and its seeds. These seeds are very much mature and more of a yellowish green color. These could be picked now or you wait longer if you desired. One thing to note is that in the seedhead on the far left, none of the seeds were fertilized and all you have is brown fluff. Even on the seedheads where there are fertile seeds, you can see vacant areas where the seeds didn't develop due to not being fertilized.

{{gwi:587928}}

In the last picture, you see at least three seeds on my Sunset clematis that have been fertilized and are a light tan color. These could be picked now. One of the three mature seeds is at the six o'clock position and the other two are at about a 45 degree angle up towards the left.

{{gwi:625771}}

Just recently, Brian Collingwood, who infrequently visits this forum and is a clematis grower extraordinare, was asked about seed harvesting on clematis and this is what he had to say:

"In my very basic amateur experience, as long as they are reasonably fully formed, it is no problem to pick seeds green. If you pop them into a dry paper bag for a week they will usually harden and turn brown. I've had to pick green seeds several times; sometimes you've no choice, it's a matter of saving them as best you can. But most seeds I've planted, which have been picked still green and then left to ripen for a week, have generally germinated with the usual frequency. I suppose there are exceptions, and definitely one should of course avoid picking them too early, but as far as I am aware, things should usually be ok, as long as they are quite near close to natural ripeness. I once had a conversation with a well-known breeder, and he used to deliberately pick seeds of some of the viornae green, explaining that he seemed to get better germination that way. I've never really found the need to do that myself, but I certainly have had good germination from seeds formed and picked late in the season, where I have had to harvest early, because that is the stage they were at, when the weather/cold coming on made it a necessity. This year I have a couple of cross-pollinations still on the go, in the house, I will have to pick them green because I don't want to lose them - I did some crossings late, this year, and only had a little time left for the seeds to form."

His statement certainly seems to debunk the myth that clematis seed have to be brown to be mature enough for picking.