We planted several pygmy date palms last March. They looked great all year. (Well, they took a hit during our hot summer with the frond tips turning brown with sunburn.) But we didn't realize that they were so susceptible to the cold and left them uncovered a couple of nights during the freeze. After that we covered them with sheets. Now the top fronds are brittle and dead. The stems are still pliable and some are green. The new growth that had begun to come out in the late fall is brown and appears dead. The lower branches are green. I live in Scottsdale. They look like they will survive, but do I trim out the dead limbs? Wait until new growth starts sprouting from the center again?