Well, not just from seeds. Flowers also grow from corms (think freesia, gladiolas), tubers (dahlias!), and true bulbs (tulips, daffodils).
More importantly, commercially grown flowers come from all over the world. Kenya, Ethiopia, Ecuador, and Tanzania account for 98% of certified Fairtrade flowers.
Columbia is the 2nd largest producer of roses after Ecuador with high altitudes and cool nights near the equator. The Netherlands is the largest center for distribution. Flowers also come from South Africa, New Zealand, Israel, and all over Europe.
Growers harvest and box ship to importers and wholesalers, who then ship to florists and other retail outlets. Some flowers travel up to 6 days out of water!