"For light frosts, cover the plants with floating row covers, or even old bed sheets or towels. This usually helps. For a hard freeze, these won't work."
Dave Dewitt is the author of several books on chiles, including The Pepper Garden Book
Believe it or not, however, there is a web site all about horseradish at http://www.horseradish.org
Our hot section is at http://www.hotsaucecatalog.com/extreme-heat-10/