Never collected these, nor grew them, but it appears a bit early since there are still some petals that are purple. Sacrifice one, crush it, and see if the seeds inside are dry.

Rodney

These are called Bachelor Buttons. You need to let the purple flowers get brown, then pick them and save them until spring. Your flower is the seed and there are LOTS of them. Or if you do not mind more baby plants just them fall and hey will come up in spring.

these are gomphrenas not bachelor buttons

I had the same thought and looked it up. I discovered that BB is also a vernacular name for Gomphrena globosa. This just goes to show how very confusing and unhelpful common names are if you are trying to find out about a plant. The OP used the correct name and would do well to stick to using Gomphrena globosa when seeking reliable information. There are at least 3 completely different plants which get called BB.

I hate common names :( I'm doing my best to learn all botanical names of the plants I grow.