I'd have to echo the "beware" when it comes to dwarf firebush. The dwarf refers to the size of their leaves, not the plants. I have a lovely split-leaf philodendron next to the pool. Doesn't provide any sort of value to any wildlife, but it looks great and doesn't trash up my pool. I also have a chenille, which doesn't shed its flowers too badly, but I'm not sure how well it would do in that kind of blazing sun. I like the firespike idea. Not messy, butterflies love them, and they're not picky about water, sun, pests. But you need to love them because they will take over that entire planter. They root wherever a stem touches dirt, so they spread quite easily. They're really perfect for a planter like that, where they can't get out of control and take over the yard, but only if you want to give over the planter to them. Maybe with a split-leaf philodendron or two to give you some texture - they couldn't fight it.

The term "blogging" has derivated to include the frequent participation in web forums, so spmimi you are indeed a blogger. Blogging has also come to include the development of a 'language' unique to the Internet, including acronyms, abbreviations, abstracted grammer and a stream of consciousness writing style which may very well avoid or omit proper capitalization and punctuation. So chuckie, if you are truly familiar with the term you shouldn't be surprised or feel the need to make criticisms that contradict the terminology. spmimi, I wouldn't be overly concerned about poisonous/toxic plants - plants exhibiting some degree of toxicity far outnumber those that do not. With few exceptions, toxicity is limited to actual ingestion of plant parts - those that may cause skin reactions to sensitive individuals are very limited and typically well publicized. So just don't graze through your garden and you should be fine! Choices for taller plants for a shade garden include those metioned above (btw, foxgloves/Digitalis are also quite toxic if ingested), as well as Ligularia, Thalictrum, Aruncus (goatsbeard), Japanese anemones, some species of Tricyrtis (toadlilies) and various astilbes.

One thing I do recommend is that you research before you plant anything. Some water/creekside plants are invasive and will crowd out native plants. When this happens the wild life that is dependant on that particular food looses its source of food. I live by a creek and wetlands so I try to plant natives along with plants I know wont be invasive. I'm also zone 5. Ligulara loves wet areas and likes morning sun.My Astilbe is doing great on the creek bed. So are hostas. We have native skunk cabbage which to me is just as attractive as Hostas, so I leave them. Lilies will do good if they get sun. Blue flag Irish does good on stream banks if they are getting sun, The Yellow flag iris is more invasive. I love living by the creek, ours is small and sometimes dries up. We also have a couple ponds. ITs fun to watch the wildlife and waterlife.

I can't tell how much room there is between them, but some ideas: a medium height white phlox a medium height Delphinium one of the taller dark-leafed perennial geraniums a purple-blue clematis, integrifolia group/nonvining, something like Sapphire Indigo, or Twinkle, or Blue River that gets 3'-4' tall a cream-colored daylily such as Joan Senior Nicotiana is an annual, but comes in shades of white, red, pink, pale green Nepeta, especially if you use Thyme2dig's strategy of using short supports to keep it from flopping. Or even divide the phlox and/or the daylily so you have larger patches.