Nancy, here we call cilantro, coriander. It's a bad sport of a plant, it bolts to seed really fast especially in summer and makes yo feel a failure of a gardener. You need to consider the plants to be semi-disposable, especially in summer. If you let it set seed, then let the seedlings grow where they are, you should have a steady supply of coriander (cilantro) for summer. But you need to use it regularly. Any herb - use it or lose it, because eventually when just left, they get straggly then flower, and once ANY herb flowers (well, most of them) they set seed and die back for winter, even if it's not winter yet.
So pinch back any shoots beginning to develop flower heads, until the end of the season. You need to be increasingly vigilant as summer progresses. Basil is a good plant to teach you how to manage pinching back the flower heads. Every time you pinch back a flower bud, that shoot becomes two shoots. It doubles exponentially, so after just a week you can have 16 more shoots.
Use for mint - if you find you're pinching it back faster than you're using it, hang it up to dry, then crumble the dried leaves into some mixed herbs. Sprinkle this mix onto a leg of lamb before roasting, or onto a Greek salad. Or mix it into meatballs and serve them with tzaziki, a Greek yogurt/cucumber/garlic dip. Otherwise - add fresh mint to peas before cooking, or add it to drinks (chop it and add it to water in ice cube trays, then toss a minty cube into your sangria) or make a mint/cinnamon syrup to keep in your fridge and use as a base for some great drinks as you head into the colder weather.
My best friend had a reputation around town as being a really bad gardener. "Don't ever give her a plant - she kills artificial flowers!"
I gave her a LARGE self-watering tub of herbs which I planted up for her myself. The secret to potted herbs, is make the pot a large one. Small pots dry out too fast and the best of gardeners tends to kill them. I also made sure to not include any mint plants in the big tub - I put in rosemary, basil, parsley and oregano. Every time I visited, I would nip off the flower heads and show her how to do it. Over time and with me showing her, she learned. She has become quite a good gardener, still fairly clueless but her deck is now covered with some beautiful plants.
At the moment I am no master gardener. My vegetable bed is full of weeds and the vegetables I planted have all died off for lack of care. I need to get out there and weed, big-time, then re-plant.
Marg