hii want to grow some begonia illuminationsin my window boxes on my balcony

Though the majority of Begonia's are shade lovers and will simply scorch in full sun, many of the species used for bedding purposes are derived from more sun tolerant species such as this one. The stems can be brittle and are best if not too exposed so you may need to provide a little help there. Can the window boxes have trellis attached at either end? (not flat on the wall but flat against the but end of the window box). If the trellis went down to a container on the floor of both, you could put a quick growing climber up each to help break the wind.