Growing Wasabi at Home

15 Aug 2020 - Jason Schlesinger

Wasabi is a close relative to horseradish, and a cousin to broccoli which is used culinary in Japan. If you’ve ever had sushi, sashimi (sliced, raw fish), or soba noodles (cold, buckwheat noodles) then you’ve probably had some green paste along with it. However, if you are outside of Japan it is most likely this was green-colored horseradish instead of true wasabi. The reason for this is that there is only one major grower of wasabi in the United States: Oregon Coast Wasabi. They sell wasabi, products made with wasabi, and, most importantly, wasabi plant starts.

What’s a Rhizome?

The entire wasabi plant is edible, but the most prized part of the wasabi plant is the rhizome. Rhizomes are like a cross between a stem and a root, and can serve multiple purposes in a plant. Some examples of rhizomes are turmeric and ginger, which form rhizomes which we use as spice. These rhizomes act as both storage organs, but also support vegetative reproduction which means that the plant will grow new clone plants out of the rhizome to propagate itself.

The wasabi rhizome has high concentrations of complex chemicals which gives it its unique flavor. It’s believed that the wasabi plant produces these chemicals to inhibit microbial growth.

Growing Your Own

About a year and a half ago, I purchased three wasabi starts from Oregon Coast Wasabi. I read up a little bit about growing wasabi, but there was not that much information out there. One thing I found surprising is that most of the guides I read suggested to grow wasabi in soil, but everywhere I’d seen wasabi grown it was grown almost hydroponically. Since I was on a hydroponic kick at the time, I decided to pop my starts in some expanded clay pellets with some very dilute nutrient solution and see what happened.

Almost overnight the starts had grown more roots and were putting out new leaves. Things seemed to be going well, and as long as I kept the tin I was growing them in topped up, they were happy.

Problem 1: Dehydration

I had gone away for a little while, and while I had given them plenty to drink, I hadn’t noticed the aluminium bread tin I was growing them in had sprung a leak. The plants sat dry for several days and all their leaves died. The rhizome was the hero which came to the rescue! Because it is a storage organ, it had plenty of carbohydrates stored up for when I got back and started watering the plants again. All but one of the starts started growing new leaves, and one of the plants even started budding a daughter plant!

Problem 2: Over-Nutrition

I got pretty lazy about giving the plants any nutrients, and they were living on pure mountain spring water Portland tap water for several months. Eventually they protested and the leaves started yellowing from nitrogen deficiency. I gave in and slowly started ramping up the nutrients to normal levels. The leaves went green almost after the most dilute dose of nutrients, but as I got closer to the recommended levels of vegetative nutrient concentration, the leaf tips started showing signs of nutrient burning. I backed off on the nutrient concentration but the damage had been done. One of the plants started dying and began rotting in the container. All in all I lost all but two plants.

Lessons Learned

If I did it again, I would use either an ebb-and-flow, or NFT hydroponic system rather than just dumping water on the plants as if they were in soil. This would prevent them from rotting, keep their roots aerated, and allow me to keep a much closer eye on their water supply. In addition, I would actually start with more than three plants. It can take up to a year or two to get a serious rhizome fit for a sushi restaurant, but a rhizome of any size can still be harvested for culinary purposes. I definitely picked off a few smaller rhizomes when I had the urge for wasabi. Since the plant readily propagates asexually, it would be easy to have way too many wasabi plants after a few years.

However, I don’t think I’ll be growing wasabi again any time soon. I had a good time, but in the end even with the minimal effort, it was more hassle than it was worth. I’ll just go with the green horseradish in the squeeze tube from now on.