Watered believe it or not. The best solution is to WATER with an oscillating sprinkler BEFORE morning. Watering like this actually slows the already frozen cells in thawing. Fast thaw is what kills most plants or plant material subjected to a freeze or frost. Watering slows the thawing down. Healthy plants will be able to recover. So yes, water them. Get up in the dark mornings to check your garden for freezing. If there was a freeze and you've got frozen plant material start watering. Seriously, this slows the thaw process down so that there are less plant cells bursting when those cells go from frozen to thawing.. I barely got out there to water but only the tops froze. Plenty of foliage to continue to make potatoes. I just lopped the ruined foliage off.
BUT WAIT! You've got to get some 'row cloth' to wrap your babies in BEFORE night time and the chance of freezing. This stuff, white, permeable to water and light...is a gardener's best friend. Also stops insects during the time they want to lay eggs on or near your plants. Just dump soil all around the edges so the flies or moths are unable to crawl beneath.
This row cloth is purported to maintain temps that are 10 to 20 degrees higher than the outside temperatures. Plants in pots are very susceptible to cold and freezes...the weakest part of plants are first; the deciduous leaves which usually abscise to fall and depart the plant to protect the plant. The next are the roots. In a pot, plant roots are terribly unprotected from cold. If the frost or freeze is no big deal plant roots should do fine. For very sensitive plants or plants planted in pots left out side in an exotic zone (tropical plants trying to endure non tropical zones and temperatures) I have used heated wraps, Christmas lights and lots of burlap to allow those plants to survive a few too cold nights...wind. Row cloth on the potatoes in my picture would have not allowed those leaves to freeze. I forgot to deal with freezing that night. Bummer but not a deal breaker. ROW CLOTH. Gotta have it to extend your seasons and protect from sporadic freezes!