dahlia

Have you grown them from seed. If so they are most likely annual dahlia's. I don't know whether you can save the seed but you could try. If not wait until frost blackens the foliage then dig the whole lot up turn upside down & store in a frost free shed/garage for a couple of weeks. Shake off all the soil & then pot up in trays of compost up to its neck & keep frost free all winter. In early spring water sparingly & new shoots will appear that you can use as cuttings to start off new plants + you can repot the old tubers & then plant out when all danger of frost is past.

The pointed looking buds are the ones that have already flowered (round ones are still to come  )

If they are annual ones, then just let one or two of these mature and dry off, then pick them and keep them until they are completely dry.

You can sow them next spring, in warmth, about end of March.

Other dahlias also set seed of course, not just annuals, but might take longer to get to flowering size from seedlings.