This will help them come up faster and ensure a healthy plant. Cold and wet conditions earlier may cause them to rot. If it seems like it takes forever for your caladium bulbs to come up you are probably planting them too early in the spring.
Late spring is best.
You need to buy them early however to get the best selection. There should be quite a few potted plants available later however. You can store them in a dry warm ventilated area on flats or hanging in mesh bags. You can replant in spring when the weather is warm. This will save them from rotting in the ground due to cold wet conditions.