Linked from
The 9 pages that link to Horseradish, each with the reason it gives.
MustardCompared with: It delivers a similar nasal sting through different plant chemistry.
Mustard oilRelated: It produces the same principal volatile pungent compound as many mustards.
DaikonCompared with: Its intense heat contrasts with daikon’s mildness, though both can be grated.
Henry J. HeinzBroader topic: Heinz first sold horseradish prepared from his family’s garden.