Aggie, once a year, in Spring. They set their flower buds in late summer - those buds produce blooms the following Spring.

I have some doubts about their long-term success in Texas (any part). Rhodendrons don't like HOT and DRY (nor arctic cold). They prefer it cool and moist (think the Pacific Northwest or East Coast zones 6 and 7). I would plant them in either a northern or eastern exposure or an exposure that offered some protection from the sun. Mulch and keep well watered while they root in. Like azaleas, they love acid soils. Give them a try, I love them! PS. For me they bloom in May. Roseum elegans is my favorite.

The American Rhododendron Society convention is in Tulsa, OK, in 2 weeks. They have found quite a few rhododendrons that do well in Texas and Oklahoma. They are mostly some of the same iron-clads that do well in severe cold climates such as Roseum Elegans.