My parsley doesn't produce seeds until late October, and then I take the seeds off and sprinkle them where I want them to grow the next spring. Parsley is the only herb I do allow to go to seed. My dill is planted in the garden.

I have a 5 foot square herb garden on the front corner of my back yard. The north and east sides are boxed in with our fence so I have a couple of stepping stones for access. In the center, but more to the back I have a square block of stone, just big enough to hold an urn.

The oregano and sage are in the back corners. Chives are in front of the Oregano and parsley going to seed in front of the chives. On the other side is this years parsley and basil and the basil or nasturtiums fills in whereever there is a space. The parsley and basil move back and forth from side to side. The south and west sides have marigolds along the edge.

The urn in the center holds Rosemary and whatever else I decide to put in there. It may be flowers or some other herb.

I don't grow thyme. It's a herb I almost never use and I found it very invasive.

Anyway that's my herb garden. I think it looks attractive besides being useful

Herb self-seeders in my gardens that are coming to mind include dill, fennel, calendula, cilantro, borage, catnip, lemon balm, sage, asparagus, egyptian onions (not exactly seeds, but close enough), chives, garlic (again not exactly seeds), chamomile, echinacea, raspberry, strawberry, motherwort, clary sage, elecampane, st. johns wort, feverfew, etc....

Just let the plants drop seed themselves and you'll have new plants next spring. In the spring just move the new volunteers as you want or clear some out to keep your garden tidy, yet full. This works best if you are not an overly fussy gardener. If you are, clip the mature dried seed heads, collect seed, and sow in a more orderly fashion.

FataMorgana

ohoh, I grew clary sage this year and wondered if it would self sow. I'm not sure I like it but a few plants got very bushy and looked nice next to echinacae. Since I compost I've found interesting things coming up when I don't expect them to. I have bok choy growing around a recently planted crab apple. Calendula seems to be especially good at growing anyplace including the crevices between bricks. I should do a better job of deadheading them but I think they add some nice color to all the different shades of green in an herb bed. I would recommend, however, that you also save some of the seed to put where you want it next spring. In a new and not full perennial bed I let a patch of calendula take up some space at the front edge. The bed also got some dill, a marigold and nasturtium from who knows where but probably the compost or birds are to blame. With experience you will recognize the seedlings. I can't seem to grow cilantro. It does better as a volunteer.

I have a holding bed behind the house which I can see from my computer. I need to get the last of the "temporarily planted" perennials moved to a proper home. In the meantime, goldenrod, brown eyed susans have joined the echinacae to the delight of goldfinches and other birds. It's wonderful to watch them going after the seed.