Q.How to treat plants that are damaged in a light frost
We recently moved to the TX Hill Country. We have morning glory that I know will survive our mild winters but I’m not sure whether I should trim the plants back immediately and cover the pots with straw or let the rest of the plant freeze (or die back) before cutting. I seem to remember that some bulbs do better if you let the plant die back naturally but I can’t find any written material to support that idea.

It's true that most perennial and bulb plants will do better if the foliage is allowed to die naturally before cutting.This allows the plants to draw nutrients from the leaves as long as the leaves are still green. If the leaves turn brown and appear dead, then you can cut them back and cover with straw, even if there hasn't been a freeze yet.