Cut the bacon into matchsticks. Render it slowly in a frying pan and then cook more quickly to allow it to crisp. Quickly wash the greens and shake or towel them dry. Tear the spinach into manageable pieces. Place it with the rest of the leaves in a salad bowl. Pour on the hot bacon and its fat and toss quickly. Sprinkle on a little cider vinegar and serve immediately, adding oil if you think it needs it and scatter on the flowers. For a vegetarian salad, omit the bacon and simply dress the salad. Edible flowers in season will provide a decorative extra.