It needs to be now lower than about 60 degrees at night. 45 is much too cold. I don't know anything about your area, but I don't give as much credence to the air temp as the soil temp. My soils don't warm up soon enough, so I start indoors in containers.
Caladiums planted about a month ago are starting to sprout and grow. Still awaiting an elephant ear to sprout. It has been so warm that I take the kids outside for a romp :) during the day and then put them to bed in my kitchen at night. I can't wait for warm nights!
So are the bulbs wasted ? Do they rot in the ground ? Do I just wait it out for warmer weather? It is mostly shaded there also. When I planted them it was in the 60's at night but it has gotten cooler since then. That's Arkansas weather for you.