Leopard Lily Flowering

We bought your leopard lily (Belamcanda chinensis) several years ago. It is growing and leafing beautifully, but has never flowered. Can you tell us what the ideal growing conditions are?
Are only the flowers used for medicinal purposes?

The plant likes full sun in good, but well draining soil. It will even succeed in poor sandy soil. It has bloomed for us in our zone 5 gardens.
It is the rhizome (fleshy root) that is used medicinally as an antibiotic (not for pregnant women)