This article and photos is by Jennifer Rensenbrink and appeared in the May/Jun 2020 issue of the Northern Gardener
I love to eat prepared horseradish—I’ve put scoops of it on everything from roast beef to bratwurst, and it gives a nice oomph to my deviled eggs. After reading that the plant also repels potato bugs, I decided to grow horseradish at my community garden plot, which had been plagued by bugs. I’d also read that horseradish can be an aggressive plant, so I proceeded with caution.
Here’s how to grow it, how to keep it in check and, most importantly, how to make it into a tasty condiment that keeps well in the freezer.
I bought two tiny horseradish plants in 2014 at a plant sale. They thrived that year, bookending a row of potatoes in my sunny community garden plot. I did not harvest any roots that fall because I wanted to make sure the plants survived the winter. I laugh at that now, knowing how indestructible horseradish is.
After my plants were established, I began to see just how big they would get, and how quickly. Each plant grows 2 to 3 feet wide and tall, and they love to spread. Horseradish plants spread in two ways: first, they get flowers that set seed. Pollinators love the flowers that come in early June, and they’re pretty! I usually leave them on the plants until they’re done flowering but not all the way out to seed. Then I cut off all the spent flowers and compost them. This is the first control method.
The second way that horseradish spreads is by its roots. Some of the roots grow straight down, almost like a carrot. But some of them take a sharp 90-degree turn and start spreading underground, sending up new vertical shoots. This is the second way that the plant expands its territory over time. We control this aspect of horseradish by making sure we harvest every year.
The best time to harvest horseradish is in late fall—preferably after a good frost. Harvesting is a little bit like dividing a perennial, such as a hosta. You spade down as deep as you can in a circle all the way around the plant. If your plant is large, spade through the middle, too, so you have manageable clumps to work with. Dig up as much of the plant as humanly possible, because small fragments of root will break off in many places, and they will pop up next spring. You will not kill the plant. I promise.
Lay your roots down nearby and take a look at them. Some of them will be about the size of a pencil. These don’t yield much after peeling, so I replant them for next year. Just dig a few holes and drop them into the spot where you dug the whole thing out. Those roots, plus whatever fragments you accidentally broke off when you were pulling the roots out will help you grow horseradish next year.
Nice young roots—similar in size and shape to a carrot—are easier to process than larger, tougher, older roots. These days, I get such an abundant harvest that I compost some of the difficult older ones.
Now comes the fun part, but first, a very strict warning. You must (like really, really must) process your horseradish outdoors. If you do it inside, you will be running out the door within five minutes, tears streaming and lungs burning. The gas that is released when horseradish is grated (by hand or in a food processor) has effects similar to tear gas.
I wait for a nice day, usually in October, to process my horseradish. After pulling it out (you could store it in a plastic bag in the refrigerator for several days before processing it), wash it thoroughly and scrub off as much dirt as you can.
Next, peel and chop your roots. This is easier said than done because they can be quite knobby, but do your best. With a sharp knife, cut your roots into 1- to 2-inch pieces if you’re using a blender or food processor. Leave them closer to carrot-size if you’re grating by hand.
Now it’s time to grate your roots, and this is the time it is critical to be outside. I’ve done this two ways. You can grate them by hand with a fine cheese grater, or you can use a high-quality food processor or blender. If you use a machine, add a little water to each batch you process. I make a lot of horseradish every year, so I’ve switched to using a blender.
Your horseradish will taste hotter the longer it’s exposed to air. If you have a large amount to process, you have a choice: grate it in small batches, then finish and squirrel each one away in a tightly covered jar, or say to heck with it and let your big bowl of grated horseradish sit there getting hotter and hotter until you’re done grating. It’s up to you.
Either way, after you’re done grating, add 1 healthy pinch of salt and a nice splash of white vinegar (1 to 2 tablespoons) for every 2 cups of prepared horseradish. The vinegar slows down the chemical reaction enough that you can now take your bowl of prepared horseradish inside, taste it, and add more salt and vinegar as necessary. Then transfer it to half-pint jars for storage.
If it’s a little on the dry side, I like to add more vinegar at this point so that each jar is at least half full of liquid. The total amount of salt and vinegar that you add can vary according to your taste. Your prepared horseradish can be eaten right away, or it can be kept in the refrigerator for up to two months. For long-term storage, freeze it and it will remain good for up to a year.
Landscaping with Horseradish
As a garden plant, I’ve come to appreciate that you can grow horseradish for looks too. I divided one of my two community garden horseradishes a couple of years ago and added a new clump to the wildflower garden in my front yard. The plant is in part shade, so it doesn’t produce many flowers—one less control practice to worry about. It provides a nice, solid green, structural backdrop to my wildflowers, yet dies back to the ground in the winter. I don’t need to worry about shoveling snow onto it or protecting it from rabbits. The tender, early-spring leaves are edible.
I’ve never noticed if horseradish actually repels potato bugs, which was the first reason I planted it! But I’ve never seen a potato bug in my community garden plot since I added it there, and I grow potatoes every year.
If you’re ready to commit to some control practices, horseradish makes a great perennial addition to a mixed edible landscape or a vegetable garden. Or both!
Jennifer Rensenbrink grows wildflowers, vegetables and fruit in her tiny south Minneapolis yard as well as at a local community garden.