Notes on Growing H. ulmarius

RushWayne rushwayne at
Thu May 1 11:46:03 EST 1997

 I have been growing Hypsizygus ulmarius (the
white elm mushroom) at home for over a year now, and 
I wanted to share some of my experience with this 
species with other mushroomers.
      The strain, DAOM 189249, featured in Paul Stamets 
book, comes from the Canadian Department of Agriculture.
It is fast-growing, visually attractive (resembling large
white flowers), and quite flavorful, especially when
young.  It gives good yields (in the neighborhood of 
100% biological efficiency), green mold contamination
of mature cultures is extremely rare, and it is fairly
resistant to fungus gnats, although they are attracted
to the fruiting bodies.  I have grown this strain year
round.  The cultures get up to 80-85 degrees F in 
summer, and the fruiting room (my basement) gets down
to the high forties in the winter. 
     On the negative side, Hypsizygus ulmarius puts
out large amounts of spores at maturity;  the mushrooms
are relatively fragile (like oyster mushrooms) and they
do not store for longer than about 4-5 days.  The stalks
vary in their edibility, often being quite tough.
     I maintain H. ulmarius on MYA with rabbit chow
pellets and sawdust added, as well as a bit of flour of
wheat, rye, corn, brown rice, oats, or millet on rotation.
The agar plates also contain added hydrogen peroxide to 
prevent contamination.  The peroxide kills all airborne 
contaminants while allowing healthy growth of the 
mycelium (plug: I sell a manual on Growing Mushrooms 
with Hydrogen Peroxide, available from me for $20 plus 
   I make spawn out of a mixture of sawdust, Crown
Animal Bedding, and rabbit chow, and inoculate this with
agar wedges.  The spawn is usually ready to use in two
weeks, at which time I break it up, let it sit 24 hrs, then
inoculate it into sawdust made from boiling-water-
reconstituted wood pellet fuel.  The sawdust also gets
hydrogen peroxide added (as does the spawn medium) to
prevent contamination.  I add commercial wild birdseed
mixture (pressure cooked for 1 hr 15 min) as a 
supplement, at a rate of 10-20 percent.  
     I pour the inoculated substrate into "tall kitchen bags"
straight out of the package, placed inside of small boxes,
twist the mouth of the bag closed, and incubate at 
room temperature.  (I use roughly 5 pounds wet weight 
of substrate per bag).  Cultures are usually grown through 
in two to three weeks time.  
     Primordia form on the top surface of the culture after 
4-6 weeks or so, depending on the kind of sawdust.  
(Primordia will also form, somewhat earlier, at the site 
of bag punctures on the side of the culture).  I gradually
open the bags as the primordia enlarge, eventually
placing the block with its young mushrooms under a
spray set-up controlled by an inexpensive watering timer.
H. ulmarius benefits from high humidity and plenty of
spray.  The mushrooms are mature when the margin of
the cap flattens out.  Clusters weighing up to one and 
a half pounds can then be harvested.  Second flushes
weighing typically about one half pound follow in about
two weeks if a slit is cut in the side of the bag and the
surface of the culture is scratched.  (Although the cultures
will form primordia again on the top surface after the first
flush, these virtually always abort).  Additional flushes
can be produced by soaking the blocks overnight in water
and re-bagging, then placing a new slit in the side of the
bag as a focus for primordia formation.     
     This mushroom can also be grown on straw using
grain spawn.  Primordia form sooner than on sawdust,
but the resulting clusters fall apart more easily and the
mushrooms tend to be smaller.
     H. ulmarius has an extraordinary flavor when harvested
young, but it is also quite good when mature, much better
than P. pulmonarius, for instance.  I like to sautee until
brown at the edges, then add to almost any dish that uses
mushrooms.  They are terrific on wheat toast (the 
toast counterbalances the oyster-like texture, which I find
gets tiring after a while), and they probably could be built 
into a good sandwich with cheese, tomatoes, and sprouts.  
--Rush Wayne

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