If you want your herbs to keep going, you must cut them back, so that provides me with lots of options.
And if you don't want the plants to go to seed everywhere you must remove the spent flowers. I think the seed heads are beautiful in a very architectural kind of way. These are the seeds from my columbines. Once they are totally dry you won't want to bump the table! I take the bouquet when I'm done loving it and turn it upside down in a brown grocery bag and shake. You just collected all the seeds, and now you can package them in little packages and share with your friends. You may even want to save the stems for the fall when the flowers are pretty much done.
Poppy seeds are my favorite. When I was a little girl my next door neighbor planted lots of poppies and showed us how each little head is like a salt shaker. These will get emptied and saved for adding to other dried floral arrangements. I am anxiously awaiting my white hydrangea's turning a light papery green so I can harvest my winter bouquets!
To be interested in the changing seasons is a happier state of mind than to be hopelessly in love with spring. GEORGE SANTAYANA
Enjoy your day!