Horseradish (Armoracia rusticana) is a member of the Brassicaceae family which includes mustard and wasabi, plus other less potent plants such as cabbage and cauliflower. It is grown for the root. It has a very distinctive though hard to describe flavour, very different from mustard.
When fresh it is really, really hot. However the heat fades over time, even in sauces where vinegar is used to preserve the taste. If you’ve chopped horseradish by hand you will know that its ability to bring tears to your eyes is way more than onions!
Foliage is similar to that of the broadleaf weed Dock, but with no colouration other than green.
It has a reputation for being invasive that is only partly merited. It spreads by sending new root shoots out laterally, and when grown in good conditions it does this a lot. However, growing separated from other plants by a strip of well mown lawn is all that is really needed to control it.
We have found it can be susceptible to white butterfly caterpillars, though once well established this becomes less of a problem. In long dry summers it does like a bit of watering. The foliage dies off over winter.
Conventionally it is harvested in autumn, but it can be harvested at any time.
Thought to be of Mediterranean or Eastern European origin, the English name “horseradish” is considered to be a coruption of its German name, Meerrettich (badly prononced as “mare radish”). An alternative explanation is that horse is being used as with some other English plant names to denote “strong”. Either way, it has no particular association with horses!
Growing horsradish for us is more of a hobby than a commercial crop, and we have a relatively small plot of it.