Why Does My Lettuce Freeze?
Can anyone offer insight as to why my lettuce and celery, always stored in the identical way in the identical crisper drawer of the identical refrigerator, with absolutely no adjustment to the temperature and no environmental changes I can think of, sometime are just fine (nice and crisp) and other times freeze hard and have to be thrown out? I can't discern a pattern. I wash lettuce and celery after I buy it, drain it on a towel, then store it wrapped in a big linen cloth (I cut up an old linen tablecloth to make four big squares just for this purpose). How do restaurants store lettuce?
I would get a thermometer for your fridge to see what temp it is. It's probably a little cold. Maybe it only freezes sometimes based on what else is in the fridge? Is it harder to keep lots of stuff cold? Or a little bit of stuff cold?
"I would get a thermometer for your fridge to see what temp it is."
Right. The fridge obviously isn't maintaining as even a temperature as the OP apparently thought it was. Placement/organization can affect airflow, which can dramatically change "microclimates."
Unless I misunderstand the OP, it seems a little weird that the lettuce isn't more prone to freezing than celery - the heavier texture and slightly lower water content should make the celery less likely to freeze. When that happens, it must be staying quite cold for an extended period.
Your fridge temp may be set just to the point where it is almost too cold. During normal operation it is fine, but when the humidity changes the fridge motor cycles more often and this may be dropping the temp the additional bit that leads to freezing.
Does your fridge have energy saving, normal, and high humidity settings? Does it ever get any condensation buildup anywhere inside during humid weather?
If so you may want to set it on the high humidity setting and then set the fridge a touch warmer than it has been and see what happens.
My crisper is colder on the left side than on the right because my meat drawer is below it and the meat drawer has a vent which can be opened and closed depending on how cold I want it too be. The cold air is vented from the freezer (side by side fridge). If I open the vent too much the left side of the crisper, directly above get more cold air and things ten to freeze. I have also found if my fridge gets too full it has colder spots and I have had stuff freeze becuse of poor circulation.
Because the celery is flat and straight, it might rest against the bottom and side where moisture could collect and/or the drawer surfaces are colder, The lettuce, being round, might have only one touch point.