2020 was a year when many of us started taking food security to heart and discovered new ways to grow edibles in our landscapes, even the smaller spaces such as townhouses and condominiums. So, I thought that I would focus on one unusual edible that has recently come to market which shows great potential for both container culture and shade tolerance…Wasabi.
Just What is Wasabi?
Wasabi (Eutrema japonicum or Wasabia japonica) is an evergreen perennial that is hardy to USDA zone 7 and a member of the Mustard family (Brassicaceae). It is native to Japan, where it grows along shaded stream banks with evenly moist soils. This plant has been used as a sushi seasoning since the Edo Period (specifically 1804-1830) and is not the ‘Western Wasabi’ (aka. coloured Horseradish paste) that often accompanies our California Rolls.
Which Parts of the Plant are Edible?
All of them. We grate the root or rhizome for the fiery paste that most of us are familiar with, while both the leaves and stems are also edible and delicious. The tiny white flowers are equally flavourful, with a peppery zest that adds gusto to salads.
Are there Different Types of Wasabi?
There are at least 20 different cultivars of Wasabi, but most of these are specific to growing regions in Japan and vary in plant form, flavour or temperature tolerance. Here in Canada, the market is relatively new, so you are only likely to find either ‘Daruma’ (excellent flavour) or ‘Mazuma’ (good for storing). I am growing a hardy strain (zone 6) that was developed from naturalized Wasabi found thriving by a cabin at the north end of Pitt Lake which is, unfortunately, no longer available.
How Do You Grow Wasabi?
By mimicking its natural environment with shade and even soil moisture that drains away. It prefers a loose, organic soil with a pH of 6-7 and a minimum depth of 6-8”. I have been growing it in a ceramic container (14” wide by 8” deep) for the past 6 years and have found the Sea Soil container mix with some added perlite (to improve drainage) to be the best growing medium. I fertilize in April with a slow-release 14-14-14 and some Gaia Green Glacial Rock Dust for trace minerals. Some growers also use Epsom Salts (Magnesium sulphate) or Gypsum (Calcium Sulphate) as either of these provides sulfur, making for a more pungent flavour.
I know of several gardeners in Maple Ridge who successfully grow Wasabi in-ground in an open-forest exposure or even in larger containers, such as half wine barrels.
Three offsets replanted in Mike's container, Wasabi Plant, Wasabi Growing in Ceramic Pot
Does Wasabi Need Winter Protection?
I am not a big believer in coddling plants, so I just leave my potted specimen to the elements. That meant that during the winter of 2016-17 when we had -5C for over 32 days the top of my Wasabi was entirely killed off, but it sprouted back with a vengeance the following spring. For those of you not willing to compromise on a pristine specimen, you could either mulch the crown a little or bring the potted plant into the garage just during below-freezing temperatures.
Are There Any Pests?
Aphids, Cabbage Loopers and slugs are the main culprits, although I just control the latter with a little organic bait. Being a member of the Mustard family, if you are growing your Wasabi near related crops such as Broccoli or Kale, then the loopers may prove to be a bigger problem, which you can control with BTK. For Aphids just use an organic pesticide such as Trounce.
Is Wasabi Good for You?
Wasabi has both anti-cancer and anti-inflammatory effects, but it also thins the blood and may slow clotting. One ounce of Wasabi contains 9% of your daily dietary fibre, as well as calcium, iron, manganese, zinc, potassium, magnesium and lots of Vitamin C; so yes, it is good for you.