Orchid Society of
Western Australia (Inc)
Thoughts on deflasking orchids and maximising
growth in compots - tips from Roy Tokunaga
by Ken Jones
I was fortunate to spend some time with Roy Tokunaga (H & R Nurseries)
on the Monday after the Conference and Show. Unfortunately, I was not
able to attend his presentation and some of the following may be familiar
to those of you who did (as I understand that he addressed many of these
issues). Some years ago, Tony wrote some helpful notes on deflasking which
are on the Society's website. The following adds to the helpful 'how to'
advice that he provided.
While I have been deflasking orchids for more than 30 years, I did not
know or appreciate the significance of some of the following. Roy told
me that his flasks are pH stabilised, to increase the shelf life in the
dark or stressed conditions.
By way of comparison, he advised that some of the flasks that he purchased
from other vendors were in poor condition when he got back to Hawaii.
He said that the flasks were 'old' and the pH was really low at less than
So what does this mean and why is pH important? pH is a scale of 1-14
that measures the acidity or basic nature of an aqueous solution, where
a reading of 7 is neutral. In this context, pH applies to the aqueous
solutions, not bark or other media. For those of you with pools, spas
or large fish ponds, you will be familiar with pH and the process of adjusting
or 'buffering' to change the pH to a level that is most efficient for
the chemicals, or in the case of the fish pond, for the health of the
fish and plants. In more technical terms, pH is a direct measurement of
the balance between acidic hydrogen ions (H+) and basic hydroxide ions
(OH-). The solution can be very acidic = 0 or very basic =14. At a pH
of 7, the concentrations of H+ and OH- are equal and the solution is said
to be neutral. For orchids, the recommended media pH is in the range 5.8
- 6.2, that is, slightly acidic.
It is also important to differentiate between alkalinity and low pH (basic)
characteristics of aqueous solutions. Alkalinity is a measure of how much
acid it takes to lower pH below a certain level (the acid-buffering capacity).
Alkalinity arises from the presence of ions that affect acid-buffering
capacity including bicarbonates of sodium, calcium, magnesium, and to
a lesser extent, sodium and calcium carbonate. By now, you're probably
wondering why this is relevant as it seems very complex. I can hear you
but I just want to grow my orchids!" Alkalinity
is important because it is more critical to managing the pH of your media
than the pH of your water. While the rainwater which I use to water the
majority of our orchids is pH 7.8 (I suspect because it is stored in concrete
tanks which would leach into the water), the alkalinity (according to
the test strips for our spa) is about 25-30 parts per million. This potentially
has a significantly adverse effect on media pH as the water is both basic
and alkaline, and as you will see from the following, the capacity of
plants to absorb critical elements necessary for vigorous growth may be
The critical thing about pH for plant growth is that if it is too low
(acidic) or too high (basic), plants experience difficulty taking up nutrient.
For example, pH values of >8 limit the availability of iron (Fe), Manganese
(Mn), Boron (B), Copper (Cu) and Zinc ( Zn), while values <5.5 limit
availability of Potassium (P), Calcium (Ca), Magnesium (Mg) and Molybdenum
(Mo). This list contains most of the essential elements with the exception
of Nitrogen (N) and Phosphorous (P) which are less susceptible to variations
in pH. What this means in practice is that we should be paying more attention
to pH, both in the fertilisers we use and the effect that they have on
our media. While it commonly accepted that some orchids, eg Paphiopedilums
prefer media that is more basic pH (for many of them, the natural habitat
is over limestone), all orchids are going to be more vigorous and make
better use of the nutrients that we provide if the pH is closer to neutral.
Clearly, those which in the natural habitat grow in moss beds will be
highly susceptible to high or low pH. Roy stressed during his lectures
that in his experience, calcium is just as important for flowering as
potassium and as important as nitrogen for new growth. It is also critical
to the development of immune response in plants against fungus and bacteria.
He recommends a pH of 5.6 for flask media. Some that I have tested recently
were 3.6 - 4.4, that is quite strongly acidic while the plants were literally
Based on the limited research of this topic undertaken for this article
and seeing the improvement in my orchids after Roy's advice about application
of dolomite lime (in just a few weeks), I have realised just how critical
pH and alkalinity are to vigorous plant growth and now know that that
I need to pay much more attention to these factors in future. Roy recommended
a series of articles by Bill Argo of Blackmore Company in USA which I
found on the St Augustine Orchid Society webpage at http://www.staugorchidsociety.org/culturewater.htm
If you are at all interested in this topic (and if you are serious about
growing your orchids well, you should be!), I can thoroughly recommend
this series of articles on pH management and plant nutrition. While scientific,
his articles were written for orchid growers and use understandable explanations
for complex concepts.
Calcium is also important for flowering. It is absorbed by the roots and
transported in the xylem at the time of flowering (note, it cannot be
stored in the bulbs or roots for future use). The xylem is one of two
types of transport tissue in vascular plants and is derived from the Greek
word xylon, meaning "wood". The best-known xylem tissue is wood,
though it is found throughout the plant. While its basic function is to
transport water, it also transports some nutrients through the plant,
particularly Calcium. Calcium is highly immobile, and moves through the
xylem with transpiration stream. If the humidity is too high or the stomatas
are closed, Calcium cannot be transported from the roots to the growing
leaves. Calcium needs to be incorporated into the cell walls and membranes
at the time they are synthesised.
So what did Roy mean by the term pH stabilised, and what is the significance
of this? In his experience, the pH of media in a flask tends to drop to
less than 4 within 5 months of sowing. From what we know about the impact
of pH on nutrient uptake, this tells us that the plants are literally
starving. Remember, there is only a limited supply of nutrient with many
plantlets competing for it, and pH at this level is such that any residual
P, Ca, Mg and Mo are not able to be absorbed by the plantlets. What Roy
has discovered over time is that many commercial flasks are calcium deficient,
particularly if they are 'old' and low on nutrient. This is even more
accentuated if the laboratory did not pH stabilise prior to sowing. To
keep it above 4.5, he says that it is necessary to buffer before sowing,
and for the final months, grow the flasks under bright light (up to 2000
ft. candles for bright light species and hybrids) to ensure that plants
are healthy. This is particularly relevant to all of us as the flasks
imported for sale at the conference were in the dark for up to two weeks
prior to being offered for sale. Therefore, it makes sense to get them
into bright light as soon as possible after purchase and to deflask while
the plantlets are actively growing.
When deflasking, it is important to use media that is pH adjusted to 6.
This can be simply done by adding Dolomite lime which provides both calcium
and magnesium to the deflasked plantlets. Roy recommends immediate fertiliser
application of calcium nitrate [5Ca(NO3)2.NH4NO3.10H2OC] at the rate of
1 gm/l (1/4 teaspoon per litre), and to avoid
fertilisers containing ammonia (NH4) for one to two months (in this regard,
you should be aware some high nitrogen fertilisers contain ammonia, or
are sourced from ammonia). This regime helps avoid black rot within the
first month of transplanting (I will provide further feedback on this
in the next newsletter as I have now used this method on more than 100
Roy chose to replate the flasks he took back to Hawaii (he refers to them
as "Dead on Arrival") because while the plants may appear to
be alive, they cannot survive out of the flask. He said that it had taken
him 30 years to figure out how to maximise deflasking survival. He told
me that on replating, 10 % of the plants died immediately reinforcing
his assessment that they could not have survived deflasking into compots.
As members are aware, we are trying to save a number of the H & R
mother flasks that would otherwise have been destroyed. Roy's advice was
to grow them for one month in the quarantine glasshouse and they will
be ready for deflasking. All his flasks are dated and will be OK for up
to 6 months in their crowded condition. He has tested some up to 12 months
but found that losses started after about 8 months.
As it will not be possible to replate them (I cannot move them out of
the quarantine glasshouse), Roy recommended that we use the method that
they employ at the nursery for their own plants. As the expense of replating
in US is substantial due to labour costs, they deflask from the mother
flasks into trays filled with sphagnum moss onto which dolomite lime has
been sprinkled. He says that they have very good results from this approach.
Given the limited space available in the quarantine glasshouse, and his
advice, I will do the same and advise the results in a future newsletter.