Caladiums in Cambria

I participated in the Caladium co-op and two dozen White Queens should arrive today. I was thinking I'd plant them under my tree ferns where they would get a little filtered morning sun but that's all. I keep that soil pretty acid for the rhododendrons, camellias and fuschias. Is it going to be too acid for the caladiums? Everything I've read says "neutral soil." As an alternative I have a trough along the north side of the house where they would get virtually no sun and the soil has never been amended. This is maybe 15" deep (looks like someone was working on the foundation and never filled it back in). I also have several bales of Black Forest soil conditioner. How much trouble would I get into if I just put a few inches of that in the trough and then covered the bulbs with 2" more? The drainage there seems pretty good as it never had standing water during the winter rains. I did some research but there was only one little bitty posting about anyone even growing caladiums in the ground in California. Am I kidding myself? Should I just pot them up, sit them in the trough and then fill in around with the Black Forest?

My clay soil has always rotted the caladiums out after the initial season. I stick to pots now.