
6 fresh rosemary sprigs, divided; plus 1 tablespoon finely chopped rosemary
1 (3-pound) fresh young whole chicken without neck and giblets
1 lemon, sliced
3 lemons, halved; divided
1 garlic head, halved; plus 1 tablespoon minced garlic
1 cup salted butter, softened
1 tablespoon lemon zest
3 tablespoons fresh lemon juice
3 teaspoons kosher salt, divided
2 teaspoons ground black pepper, divided
Canola oil, for greasing grill grate
2 (8-ounce) bunches fresh radishes, trimmed, washed and halved