Understanding Irony in Frank's Response

In a small town, there lived a man named Frank who was known for his great love of gardening. He spent every day tending to his flowers and vegetables, often boasting about how they grew better than anyone else's in the neighborhood. One day, a severe storm approached the town, and Frank was worried about the fate of his prized plants. After the storm passed, he rushed outside to see the damage. To his surprise, he found that his garden was untouched while everyone else's plants had been destroyed. Frank exclaimed, 'I knew my garden was the best!' as he stood amidst his flourishing flowers.

This scenario illustrates a specific form of verbal irony. What does Frank's reaction reveal about his character?