It depends on whether the wildflowers were planted intentionally or appeared naturally. 

If they’ve self-seeded naturally, there’s a good chance they’ll return next year without intervention. In this case, you can deadhead the flowers to encourage additional blooms this season, knowing they’re likely to reseed on their own.

The approach also depends on the species of wildflowers in your garden. Some will only flower early in summer, while others can continue into autumn. Observing their growth patterns will help you decide whether to deadhead or let them go to seed.

For a reliable display next year, consider leaving some flowers to set seed - this ensures a fresh supply of plants for the following season. Striking a balance between deadheading and allowing natural seeding often works best!