Wait for the flowers to open fully. They will turn from gray to bright purple when ready. Wait for a cool, dry time of day to harvest and bring a bucket of cold water with you.
Grasp the flowers you want to cut with your left hand, and move the nearby blooms out of the way with the sickle. Cut the stems and pull the flowers into your left hand. Continue to cut around the bush until it has been cleared. Gather the cut flowers into your left hand and the crook of your left elbow as you work.
Plunge the stems into the bucket of cold water to preserve the essential oils that give the flowers their distinctive scent. Take them inside and out of the heat as soon as possible.