Hi Wishn,
Phlox paniculata makes small med tan brown pods where flowers once were. You may not see pods everywhere. They only grow from properly fertilized flowers. The seeds are decent sized so easy to know they are the seeds. On the link below is a pic of the seeds.
Remy

Here is a link that might be useful: Phlox Paniculata Seed

Yarrow I've not collected seed of, but I did find an old post about it from people who have.
Remy

Here is a link that might be useful: Yarrow Seed Post

Yea! I collected both Laura and David seeds from my phlox. Also some pink. The pods were bursting in the sun when I was collecting them!

Good to hear!

I've learned a bit since the '05 posts...yarrow seed looks like little nails.

Hi! I collect Yarrow. They are very tiny seeds. I use scissors and snip off the ends dried stems leaving the flower heads in tact. Take them in the house and shake them in a baggie. The seeds will look very tiny in the bottom of your baggie. Or you can leave the heads on and baggie them that way. I've done that too, when my hands don't work quite right for handling the little seeds.

Last year I grew Yarrow: Summer Pastels from a seed company and they had coated each seed so it would be larger and easier to handle.

****shamelessly looking for a swap :) **************
If you'd like to swap some yarrows you can check out my trade page and see what I have and if anything interests you.

Hope this helps! vina

I FINALLY figured out what the seeds looked like after 3 tries at different times. I took a ziploc baggie like suggested, shook them up, and looked like crazy. I finally found some this time!

I took a photo of what I found so far. I was so excited that I finally found a couple, that I had to share!

I collect a lot of seeds, too. But, these two have alluded me. maybe it is simply too humid in my area?