When the flowers begin to fade, you can cut them off (a.k.a. 鈥渄eadhead鈥) to encourage the plant to bloom again. Depending on your climate and the length of your growing season, the yarrow may put out more flowers this season. Alternatively, you can leave the fading flowers on the plants to give your garden some texture in the winter months. Note that yarrow will not hesitate to spread if you allow it to go to seed, however! So if you prefer to keep your yarrow contained, then you should remove the flowers once they start to fade.
When the flowers begin to fade, you can cut them off (a.k.a. 鈥渄eadhead鈥) to encourage the plant to bloom again. Depending on your climate and the length of your growing season, the yarrow may put out more flowers this season. Alternatively, you can leave the fading flowers on the plants to give your garden some texture in the winter months. Note that yarrow will not hesitate to spread if you allow it to go to seed, however! So if you prefer to keep your yarrow contained, then you should remove the flowers once they start to fade.