The fronds that are brown will not green back up, but as long as the trunk is still healthy, it will make a new flush of fronds from the center when it's ready and that will replace all the damaged fronds. It's probably good that it isn't growing yet because when they make new flushes of fronds indoors, the new fronds tend to grow WAY longer than they should and it makes the plant look weird.

I had the same problem in my unheated garage. All my bulbs rotted and my palms definitely suffered some damage. Luckily the palms are still mostly green so they will recover and the bulbs are starting to grow back even though they rotted. Spring will definitely undo a lot of winter's damage, hopefully some nice and warm weather will get your sagos growing back nicely again. They must have been beautiful when they were green!

-Alex

Much appreciated, Alex.

They go outside next week. Will remove damaged fronds.

Any suggestions about how to care for them going forward?

Jay

Keep any green that's left on the fronds when you are pruning it since those are still photosynthesizing and it could help it recover a little bit faster. Definitely have some patience with them. They could take a while to flush, but with warm weather they should come back.

Some fertilizer could help it along also. Once days are consistently in the 70s and nights are out of the 40s, that should be warm enough for it to start kicking into growing mode.

-Alex

Luckily sagos dont mind losing their fronds. Mine defoliates every year inside and by spring it looks like a pineapple. However, it never falls to flush. I simply set the pot out and give it some epsom along with fert. Then forget about it. Just check to make sure the caudex is not mushy.

Any time you see any green in the petioles or parts of leaves, you can almost be sure the stems are fine. Give them a shot with a granular, high nitrogen fertilizer that reacts quickly, and new leaves are usually produced quickly.