Answer: Caladium tubers are fussy about moisture conditions. They won't stand drying out (they are native to rainforests), but they also don't want to sit in overly wet soil. I usually don't worry about how long bulbs take to show themselves because they usually appear when conditions are right. However, since some of yours appear to be rotting, I wonder if the soil moisture has not drained well.
In perfect conditions, a tuber may produce shoots in 7-10 days, but we seldom have perfect conditions! Caladium prefer temperatures in the 60s-70s and always need shade, especially here in the low desert.
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