That disappointed look is something I have become accustomed to, every time a young gardener approaches me for advice and asks, are there any edibles that I can grow in the shade? And while there are a few vegetables and herbs that tolerate open shade, as well as rhubarb and alpine strawberries, your standard fruit trees and berries usually fare very poorly with less than four hours of direct sunlight. Once the bad news has been regretfully shared, that look of deep disappointment staring back at me always prompts me to suggest an unlikely edible, Wasabi. At this point, they usually go for broke by asking, even deep shade? To which I reply, most definitely, after which I am almost always confronted with a hopeful grin.
With that in mind, here is everything you shady gardeners need to know about growing Wasabi.
(📸 MK Lascelle)
Where is it from?
Wasabi is fairly rare in western gardens, being native to Japan, Korea and portions of east Russia. The botanical name is currently Eutrema japonicum, although you are more likely to find it sold under its older name, Wasabia japonica. It is a member of the Brassica family, so it is related to both broccoli and horseradish (Armoracia rusticana), to which it shares a flavour palette. So much so, that the latter is often passed off as that green ‘Wasabi’ paste that comes with take out Sushi.
(📸 Pixabay)
How Hardy is It?
The species is rated at USDA zone 8, but in my experience, it has thrived in our zone 7 coastal British Columbia weather. It grows best in a temperature range of 43°F to 68°F and I know of several local gardeners who have naturalized it along shady stream banks.
(📸 Qwert1234 Wikipedia)
What Type of Sun Exposure Does It Prefer?
As was previously mentioned, shade to open shade are the ideal exposures, with too
much sun causing the plant to temporarily wilt or even scorch the leaf margins.
(Leaves Wilting in Sun | 📸 Qwert1234 Wikipedia)
What About Soil Conditions?
Here’s some great news for those of you with wet shade, as Wasabi requires wet to evenly moist soil conditions at all times. A slightly acidic pH is preferable, which is no problem in coastal BC and by adding sulfur in the form of an organic gypsum, you’ll get more pungent tasting plants.
Do They Grow in Containers?
There’s even more good news here because the answer is an emphatic yes! Although there are a few provisos, which are that you will have to be diligent with the watering, you will need to use a more compost-based soil medium (as they are heavy feeders) and larger pots with a minimum 10” depth are best. You can also shelter your Wasabi containers in a shed or garage temporarily during periods of extreme cold winter weather.
What Do You Fertilize With?
I limit my fertilizing to a slow-release 14-14-14 and some Gaia Green glacial rock dust, usually applied in April or May.
Is Wasabi Prone to Pests or Diseases?
In my experience, Wasabi has been relatively disease free with the biggest concerns being slugs and snails, who love to chow down on the leaves. So, some hand picking or slug bait may be in order.
Which Parts of the Plant are Edible?
Absolutely everything, the leaves, stems and flowers are all edible and have a mild Wasabi flavour. The rhizomes or roots are harvested 2-3 years after planting, and it is these that are used to make a pungent Wasabi paste.
(📸 MK Lascelle)
How You Cook with Wasabi?
Young, diced stems make a great addition to any stir fry, while fresh flowers and chopped leaves are wonderful in fresh salads. You can also cook whole leaves tempura-style and serve them with a sweetened soy dip, for a refreshing summer appetizer.
(📸 MK Lascelle)
When Do You Harvest Wasabi Roots?
Mature Wasabi rhizomes (about 2-3 years old) should be between 4-6” long at harvest, which is best done in spring or fall. At this time lift the entire plant and gently wash off any remaining soil. Offsets or side shoots can be carefully pruned out and put aside (with leaves intact) for replanting, while the mature stems and leaves on the central rhizome can be cut and bundled for salads and stir fry.
(📸 MK Lascelle)
How Do You Make Wasabi Paste?
Simply wash the rhizome and lightly remove the outer layer using a potato peeler. Then cut the end and gently grate the rhizome using a circular motion on a very fine or Oroshiki grater. Grate enough paste for immediate use, let it stand for 2-3 minutes to develop its hot, intense flavour but keep in mind that after 20-30 minutes, the freshly grated Wasabi will oxidize, causing it to lose its flavour.
(📸 Chris73 Wikimedia)
Can You Keep Leftover Wasabi Rhizome?
Leftover fresh rhizomes can be kept in the refrigerator crisper wrapped in damp cheesecloth or a clean towel for 3-4 weeks. To make more paste, simply rinse the rhizome off, cut off a thin slice of the blackened end and you are ready to grate again.
Well, now that you know everything about Eutrema japonicum, maybe it’s your turn to get wild over Wasabi.
(📸 MK Lascelle)
Copyright 2025 MK Lascelle
