I have several pots of herbs growing on the deck-there's oregano, basil, sage, and chives. There's also a cilantro plant that's flowered and gone to seed. I didn't know that wasn't a bad thing till someone informed me I was now maturing the spice coriander! I wasn't sure what to do with the seeds; after some research today I harvested my own fresh spice.
According to Wikipedia, "Coriander...is an annual herb. The name 'coriander' in a culinary context may refer to either the seeds of the plant (used as a spice), or to its leaves (used as a herb); however, in North American countries the name cilantro is given to the leaves." I use cilantro in Mexican food and use the leaves to garnish different dishes, so I always buy a small pot at the greenhouse when I'm buying my other plants. However, I've never been able to keep a plant going until it flowered.
I went out to the deck one day a couple of weeks ago, and the cilantro didn't look the same-- the leaves had begun to turn feathery, with a group of blooms at the top of the "new" leaves. After the first blooms, the plant was soon all feathery leaves, and covered in small white flowers, and. Some time later the seeds began to form. They started out green, and slowly turned brown.
I picked the brown seeds off the plant, and put them in a brown paper bag in the pantry. I ate a couple instead of putting them in the bag. They tasted great! According to my research, I'll be able to use the seeds in pickles, marinades, and salad dressings. I could even keep some of the seeds to try to grow my own plants next year.
For more information on coriander, try: Finished Coriander Seed Project