long-blooming bulb?

What are some other bulbs, rhizomes, or corms that have a long bloom season like dahlias?

Cannas.

Caladiums and Hosta's....I know, but they are very colorful and last until it gets cold.

Begonias are great in the shade

i have found that if i plant my lily bulbs in sun and part sun locations about the yard i get a really long bloom cycle from them. the flowers last quite a long time too if you take of the little powdery things, i forget there name, when they first open. old florists trick.

I take you are talking about tuberous begonias? I love those things! but they don't like our long rainy spells. The best ones I ever grew were in a long planter, but on a porch with a roof.

yes and i also found the ones in the planter outside did better than the ones in the ground 5 feet away. next year they all go into planters. garden and learn. :)