Trimming back Yarrow, when should I do it

I have had this yarrow for about 2 years now and it has went to seed , should i wait for them to dry out and keep them or cut them back to look better :-?

moderator's note: split this post into it's own topic

 

I have an established Apple Blossom yarrow and it reblooms when I deadhead it. And it definitely neatens up the plant

 

Margie, do you want to keep the dried seed heads for flower arrangements?

If not, plants usually do better if they are deadheaded after blooming. Their energy then goes into growing rather than into producing seed. & Bip is right, many plants will re-bloom if deadheaded.

 

I've got some that will be deadheaded over the weekend.