Where I live in zone 4, I usually plant my cannas outside from the last week in April through the end of May. Almost every year, we get a hard frost in May that knocks the cannas back that have not been covered. However, they recover very quickly and end up being just as far along as those that do not get covered.

well ... hmmmm .... you are on the right track ... but working on the wrong variables ... i am going to come at it from another angle ... hosta are VERY HEAVY WATER USERS ... and they use the most water.. in the most heat .. which is why they struggle in the deep south ... they simply cant pump enough water to offset the loss ... and part of that is ... night temps.. they can cope better up here in MI because at night it cools considerably ... hosta actually sweat ... transpire ... in england.. which is above the 60th parallel.. or 2/3 of the way to the north pole.. they are ALL FULL SUN ... partly because the sun barely shines.. lol .. but also because of the declination of the sun.. the British are a pasty peeps.. because the sun is not as strong.. so the hosta can cope ... compare that to LA.. and you can see a stark difference. .. so.. hosta can grow in full sun .. hosta are only shade tolerant.. but the sun .. or conversely.. the shade is not really the issue.... its all about how effectively they can pump.. enough water. and if they have a recovery period to cope ... the fact that a hosta looks ratty in late summer.. is more a function of not enough water.. rather than too much light ... ken ps: zone.. which is.. in its simplest form.. MINIMUM WINTER TEMP ... has nothing to do with it .... pps: i have tons of wood hyacinths.. i dont know why you failed with those.. unless there are multiple plants under that common name ... ppps: hosta also have a requisite dormancy period.. and if you go too far south.. they dont get it ...

Your lucky that it is 12". . you have some soil to work with. I have hired a friend with a jack hammer to cut in large shrubs. It made all the difference. He dug that large hole in 10 minutes. I suggest the salvia regla. It will love your soil. Blooms in spring and fall and if happy can get 6' tall. I had one go 8' but now it got trimmed back because it is by a path. I am out now in the uplands west of Austin and rocky limy bedrocky is what I have . My shade is thin shade from not very tall live oaks. I grow salvia madrensis, evergreen sumac, aromatic sumac, salvia gregii in the shade.

Recently I found out there are shade tolerant cannas.. is this true? Do you have a link for the above “shade tolerant” statement. To the best of my knowledge, all our hybrid cultivars were bred for roughly 8 hours of full sun. Yes most all cultivars will tolerate reduced time to full sun but at the expense of reaching their full potential. Cannas growing in greatly reduced sunlight must use stored nutrients in the rhizome to grow and bloom. This ultimately inhibits normal growth and over time will lead to an overall decline in general. Plants tend to get taller, bloom and chlorophyll production is reduced. Good luck, Kent