It's entirely possible that the ground has not warmed up enough. If I had planted caladiums here two months ago, it's entirely possible that they would have frozen and be mush. Caladiums are very sensitive to cold soil. Keep an eye on them, and maybe as the ground warms, they'll come on up. If they don't, you'll need to replant them when it's warmer. This probably isn't what you wanted to hear.....