ASK THE EXPERTS
After reading Dr. Lynette Morgan’s articles on growing wasabi, I now want to give it a
try. My question is, what is the recommended color temperature for growing wasabi?
Also, are there different varieties of wasabi? Or is wasabi just wasabi? Thank you!
— Richard
Q
T
here are more than 20 varieties of wasabi
known in its native habitat, Japan, where
cultivars are often region specific. In the
United States, the main cultivars grown commercially are Daruma and Mazuma, and often
these are the only ones available. The recommended cultivar for hydroponic production is Daruma, as it
can better tolerate a major disease of wasabi called black leg
(Phoma wasabiae), which is difficult to control and can result
in large losses of yield and quality. Daruma develops a thick,
green stem and has an upright growth habit. Mazuma can
be grown hydroponically, but it is reported to have a more
horizontal growth habit, poorer market quality, and greater
susceptibility to diseases such as soft rot and black leg.
A wasabi crop can be started from small plantlets, from
tissue-culture plantlets or from seed. Seed germination can
be difficult as certain dormancy requirements must be met
before germination can occur, plus seeds can be hard to
obtain. The most preferred way to start a crop is buying small
plantlets, which are offshoots produced around the crown of
the mother plant. Generally these plantlets transplant well
into hydroponic systems.
Wasabi is an excellent crop to grow indoors under
artificial light. This is because it has specific environmental
requirements and because light can be manipulated to
boost growth and yields. Wasabi is a highly vegetative crop
that grows many large leaves over a 12-18-month production
period. Although the plants often flower, blooms are not the
harvestable portions of the plants. It is the long, thick stem
of the plant that is harvested for use as fresh wasabi, and the
rate of development of this stem depends on how fast leaves
are formed and how rapidly they mature. For this reason, a
color temperature that promotes strong, compact and rapid
vegetative growth is recommended. In other words,
more of the blue wavelengths are beneficial in this
case. Start with a color temperature of 4,000°K, or
even 5,000-5,500°K, which boosts the blue portion
of the spectrum. This temperature better simulates
the natural environment of wasabi, which
traditionally grows in heavily shaded conditions
in Japan under trees on river banks.
Another factor to consider is that light intensity, particularly for young seedlings or transplants, will need to be
considerably lower than that required by many indoor crops
such as tomatoes. The intensity should be more like that
supplied to young lettuce plants or shade-loving houseplants.
Wasabi also requires cool conditions, so using LEDs will assist
A
22
Maximum Yield USA | June 2016
in preventing heat buildup and leaf burn. Artificial lighting
also allows day length to be extended, boosting growth even
further. A day length of more than 20 hours of low-intensity
light will allow maximum photosynthesis to occur, without
the issues of attempting to increase growth via higher light
intensity, which wasabi cannot tolerate.
The correct lighting intensity, combined with cooler
temperatures, optimal humidity levels (fogging or misting
may be beneficial), a well-designed hydroponic system such
as a water culture or gravel system, and even the use of
CO2 enrichment should provide you with a strong, healthy
harvest of this exotic herb.
Kind regards,
Lynette Morgan
Dr. Lynette Morgan holds a B. Hort. Tech.
degree and a PhD in hydroponic greenhouse
production from Massey University, New Zealand.
Lynette is a partner with Suntec International
Hydroponic Consultants and has authored
several hydroponic technical books. Visit
suntec.co.nz for more information.