Here's why:
* The "ow" sound in "flower" is a diphthong, meaning it's a combination of two vowel sounds. It's closer to the sound of "ou" in "house" or "cow".
* Long "o" sounds are typically spelled with an "o" followed by a consonant and an "e" at the end of the word (like "hope", "bone", "code").
Therefore, "flower" doesn't have a long "o" sound.