When does your horseradish flower? Have you ever seen it make good horseradish seed?

In the summer of 2019 after several failed attempts I finally got a hunk of horseradish root from a grocery store to sprout and grow in a container in my garden.  It flourished until the greens were killed in mid-winter and in the spring of 2020, I dug it up and found a diversity of small roots, which I divided and replanted in two containers.  They again flourished through summer and a mild winter until February, when we got polar vortexed like so many others.  Very little snow and a week of subzero temperatures culminating in a local record (-13f) cold pretty much killed everything that I normally consider winter-hardy in my garden, including all my kale and most of my garlic and onions that were in pots (although the ones in the ground seem fine).  But as soon as it warmed up, my trusty daffodils and chives sprang up out of the ground...as did my horseradish, which was entirely unexpected.  (I assumed it would straggle back from the roots later in the spring, as many other things hopefully will.)  

Weirdly, though, it's sending up a profusion of flower shoots!  It had not flowered previously.  The shoots are delicious (texture of brocolli raab but tasting of very mild mustard greens) just munching them raw in the garden, snapped off at the ground with my fingers.  I might not have thought to taste them, except some random podcast I listened to a few weeks back featured a man in Norway who claimed his horseradish (leaves and flower shoots) was the most prolific food source in his very northern garden.  

I'm interested in this development of flowers in part because I understand that horseradish rarely sets seed (and the seed is usually sterile when it is set).  Obviously I want to watch it in case it sets seed, which I will collect and test.  However, I would expect it to be sterile, because there's no genetic diversity in my patch; it all comes from a single supermarket root.  Nonetheless, I'll see.  

So, here's my question: should I expect my horseradish to flower every year, or is it a random/fluke event?  Might it have been triggered by the very hard freeze we got, perhaps stressing/damaging the roots?  The internet is all over the place, with some people saying theirs never flowers, and others saying it's rare/random, and still yet others (Hi, Skandi!) saying it flowers every year in the early spring for them.  When does your horseradish flower, if it does?

On the related question of setting viable seed, virtually all I know on that subject comes from the Experimental Farm Network, who briefly offered some incredibly-hard-to-find horseradish seed this winter.  (My timing was right to get a package before they sold out, which I am just now fixin' to plant.)  They wrote:

Horseradish is propagated almost exclusively by dividing roots of existing clones, of which there exist just a few. True horseradish seed is practically a legend... but we are thrilled to announce that we are selling honest-to-goodness horseradish seed!

We received these seeds from Austin Jones in Colorado. In 2016, Austin started 13 horseradish plants from true horseradish seed, and 10 of them lived. The plants have never been disturbed or dug up, and they have been reliably producing seed for Austin. We suspect that because these plants were propagated from true seed, and there is some diversity in his patch, they are more likely to produce viable true seed themselves. Our germination test found just 5% of the seed germinated, but we are hopeful these seeds will germinate more readily in actual soil or seed-starting mix, compared to our germination chamber. At any event, with 50 seeds per packet, we hope you will get at least a few plants, and perhaps down the road you will produce your own seed! If you ever do, please get in touch!

To sum up: I don't expect seed from my supermarket monoclonal plants, but they are flowering most vigorously and I will monitor them, if I can resist the temptation to eat all the flowers.  I would like to know if I should expect them to flower again every spring, now that they've done so once.  (My taste buds will be very disappointed if they don't.)  Meanwhile, if I get any plants from the EFN seed, I'll grow them out in proximity to the plants I already have and see if I can produce seed of my own.  If y'all have any experience with seed-producing horseradish, please share!

Hi Dan. I got my horseradish from a friend it flowers every year in spring but never has set seed. Which i don’t mind because it spreads pretty easily and i’ve not been able to get rid of it in places where i didn’t want it anymore.

Mine also flower every year I have never noticed seed since the flowerstalks don't hang around I assume it doesn't set seed.
unfortunately for me most of my horseradish has been eaten by watervoles they have killed the plants, by completely eating the roots! I have one left that the previous owner had planted in a concrete drain ring. I assumed it was to stop it spreading but now I think it may have been to protect it.

A lot of Brassicaceae species require pollination from separate plants. Assuming that horseradish(Armoracia rusticana) is the same. Doesn't help that horseradish has been cloned so many times - a lot of different varieties could just be mutants as well.

A. macrocarpa and A. sisymbrioides reproduce by seed in the wild. Unsure if they are compatible with A. rusticana - worth a try if you really want to try creating a type that produces viable seed.

Dan Boone wrote:Meanwhile, if I get any plants from the EFN seed, I'll grow them out in proximity to the plants I already have and see if I can produce seed of my own.

Did you ever get any horseradish seeds?

For almost 20 years mine flower every year. No seeds. From roots bought at a garden store so no genetic variety.

You are right, the internet is all over the place with the info regarding horseradish seeds. I have a small contained raised bed with horseradish that’s been thriving for about four years now and I’ve harvested some of the roots maybe twice. This year, for the first time, it put out the flower stalks and it’s early spring. On some website I read that you should cut the flowering stalks to allow the energy to go back into the plant and then ultimately later into the roots. I noticed that the flowers had a nice fragrance so rather than getting rid of them I took the stalks inside and put them in a vase of water. I was just about to collect them to throw in the compost because they are pretty much done and I noticed that they put out a bunch of tiny little seeds and they’re all over my table. At first I thought I must’ve brought in a caterpillar when I brought the stalks in and I thought I was seeing tiny caterpillar poop but they are in fact seeds! I’m definitely testing them to see if any are viable! I have no clue what kind of genetic diversity they have since I started them from two plants I purchased at a nursery so I have no history on them beyond that.

Thom Bri wrote:For almost 20 years mine flower every year. No seeds. From roots bought at a garden store so no genetic variety.

Oddly, mine flowered for the very first time in the 4 years I’ve been growing them. I cut the flowers and put them in water and now it’s time to compost the stalks and I see that they drop a BUNCH of seeds on my table.

Kel Dog wrote:

Thom Bri wrote:For almost 20 years mine flower every year. No seeds. From roots bought at a garden store so no genetic variety.

Oddly, mine flowered for the very first time in the 4 years I’ve been growing them. I cut the flowers and put them in water and now it’s time to compost the stalks and I see that they drop a BUNCH of seeds on my table.

I suppose I'll have to observe more carefully! They are flowering right now.