Can anyone recommend a good way to preserve fresh horseradish root?

I found a maybe 6-inch chunk of organic(!) horseradish root at the co-op
last week and ground it up yesterday with some salt and apple cider
vinegar for today's rib roast. That yielded well over a cup of knock-
yer-socks-off delicious "prepared" horseradish. Trouble is, even today
it has lost a bit of the character it had yesterday, and I know it's all
downhill from there, maybe keeping a few weeks max in the coldest part
of the refrigerator.

I've tried freezing the prepared stuff in the past, without luck. Is
there a way to preserve a section of the root so that it can be chopped
or grated as needed? The whole root doesn't keep very long in the
refrigerator before spoiling, in my experience, nor does it seem to
freeze well.

Thanks for any tips & Happy New Year.

Bob