Why is our horseradish no longer potent?
We have been growing, cultivating and eating our own horseradish for years. When we grate it you can not even take a whiff of it or it because it is so strong. That is the way we like it. We cultivated some in spring and have just dug some up now. All of a sudden we have lost most of the potency. Can you explain why?
Certified GKH Gardening Expert
I would attribute this to a sulfur deficiency. This plant is not really a high feeder, so standard deficiencies aren't as common. Sulfur deficiencies can go largely unnoticed, though.
The chemical compound, isothiocyanate, is responsible for the "spicy" in this plant. This chemical can only be formed in the presence of sulfur. This can indicate that there is a lack of this in the soil.
Try fixing this with iron sulfate, or wettable sulfur. That should take care of the issue, going forward.
here are some more tips to grow the plant: https://www.gardeningknowhow.com/edible/herbs/horseradish/growing-horseradish-how-to-grow-horseradish.htm