Propagation of cycads starts with producing and germinating
seeds. This seems to be the most difficult part of growing cycads.
Once you are working with established plants, your job is much
easier. One of the keys to producing viable seeds is the proper
collection of, and if needed, storage of pollen. I try to make
sure the pollen I use is viable. I am going to discuss how I go
through the whole process. Pollen can stay viable for at least
a week or two outside of the refrigerator. I don't recommend waiting
this long because it is important that pollen be as fresh as possible.
This will prolong its viability during storage. Using pollen that
is older is still better than nothing, if that is all you have
to work with. Pollen that has become inviable does no good and
wastes time and energy.
Cycads are dioecious (possessing separate male and female plants).
Male plants produce the pollen and females produce the seeds.
Male cones are typically thinner and taller than female cones.
Most species have a particular time of year when the males shed
pollen and the females become receptive. This timing will vary
at the same location from year to year depending on the weather.
The timing of each species will also vary depending on the location
in the world where the plant is being grown. This window of time
can be as little as a three weeks for most species, and up to
three months for many Ceratozamia spp.
Male cones emerge from the apex of the plant and grow to full
size. You can tell the cone is close to the time of shedding when
the peduncle (stem under the fertile portion of the cone) is visible.
A few days before pollen is shed, the cone will elongate and cone
scales will loosen. When I see this, I tap the top of the cone
slightly with my finger to see if the pollen falls out of the
cone. If it is a very small cone, it is best to put a piece of
paper under the cone to catch any pollen that may fall out. If
ANY pollen falls from the cone, it is ready to harvest. Stangeria
cones are the exception, and I will cover this in the next paragraph.
With few exceptions (a couple of Zamia species), pollen sacs are
located on the underside of cone scales. You will notice that
some of the pollen sacs are ruptured when you see that pollen
has fallen out. If you don't catch the male cone on its first
day releasing pollen, it is best to see how many of the pollen
sacs have ruptured. If all the pollen sacs have ruptured, it may
be hard to determine when the pollen has been released, and therefore
may be inviable. I never collect pollen from a cone that has completely
shed unless that is the only one I have to work with. If the cone
is ready to pick, gently cut the cone off and put it on a piece
of paper. I don't recommend newspaper because it is coarse and
the pollen sticks to the paper. Notebook paper works very well.
Put the cone in a cool area. Anywhere in an air conditioned house
is just fine. Extremely high temperatures will reduce the viability
of pollen. Pollen will continue to shed for approximately five
days. I collect the pollen every two days and place it in paper
packets I make by folding small pieces of notebook paper and sealing
the side and ends with tape. It is important to make sure that
the tape covers as little of the surface as possible so that the
paper packet can breathe.
Stangeria is unusual in that it sheds pollen over a three-week
period. If you cut the cone off the plant when the pollen first
starts to shed, it will stop shedding and you will harvest very
little pollen. Instead, every three or four days, hold a piece
of paper under the male cone and knock as much of the pollen out
of the cone until the three-week period is over. You may also
wait until the pollen has been shedding for ten or more days,
cut the cone, and usually the pollen will continue to shed for
the remaining time.
In order to store pollen for long periods of time, it is important
to remove as much of the water content in the pollen as possible.
Store the pollen in a glass jar or vial, avoiding plastic bags,
which can breathe and are not the best for long-term storage.
To reduce the water content in the pollen, place some desiccant
in the bottom of the container. I use an indicating desiccant.
When dry this material is blue, and as it absorbs moisture, it
turns pink. By using an indicating desiccant, you can tell when
it has absorbed all the moisture it can. It is impossible to tell
whether regular desiccant is still dry just by looking at it.
Once indicating desiccant has absorbed all the moisture possible,
it turns pink. Place it in the oven and bake it until it turns
blue again. This desiccant can be used over and over again. The
amount of desiccant you use depends on the amount of pollen you
are trying to dry out. I have found that 1/2 - 1" in the
bottom of the container works well. The paper packets are then
placed on top of the desiccant. By using paper packets, which
can breathe, the desiccant can do its job. Instead of using one
big packet for all of your pollen, place the pollen in small packets
so one packet can be removed quickly without disturbing the unused
pollen. I try to put enough pollen in each packet to pollinate
a single cone once. If you plan to pollinate the same cone a few
times, fresh pollen can be removed each time for maximum viability.
Write the species name and date stored on both sides of the packet
so you can tell later on how old the pollen is.
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| This shows a cross section of the microsporaphylls of a Zamia. The top picture shows the pollen sacks that have not ruptured yet, the bottom picture shows what ruptured pollen sacks look like. |
Two male Zamia cones. The one on the left has elongated and is ready to collect. the cone on the right has not elongated yet. |
This shows the vial, the indicating desiccant, the paper packet, and how it should be labeled. |
Once I cap the vial, I place it in the refrigerator for two days.
I do not place it directly in the freezer because the pollen's
moisture content is too high; water expansion can rupture the
pollen and render it inviable. Once the pollen has been in the
vial for at least two days, and as long as the paper packet has
had enough breathable area, moisture content will be reduced enough
for you to put the vial in the freezer. Once the vial is in the
freezer, the pollen should be good for years. I have found that
pollen will stay very fresh for at least three years. I know one
person who used pollen that had been stored for six years and
got a good seed set. I have been told that if pollen were to be
stored in liquid nitrogen, it would stay viable forever. Of course
this method is not practical for most people. If you collect pollen
on separate occasions, but eventually want to keep the pollen
in the same container, it is best to store the newer pollen in
a different vial and go through the same process in the refrigerator.
Once the new pollen is desiccated, the newer packets can be quickly
placed in the original container.
When removing packets for use, it is important to minimize the
time that the vial is open because the pollen and packets can
reabsorb moisture. This is another reason to use several packets
instead of removing a small amount of pollen each time from one
larger packet. Once you remove a packet, use the pollen as soon
as possible.
Pollen loses viability quickly at room temperature and even faster
at higher temperatures. Pollen can stay viable at room temperature
for several days, but I attempt to maximize its viability so that
more good seed is produced in the long run. Just because an entire
cone is pollinated does not mean all of the seeds will germinate.
Quality of the pollen has a great deal to do with how many seeds
in each cone are viable. Another reason to keep moisture content
low in pollen is to lessen the chance for fungus to grow on and
kill the pollen. When I send pollen to someone who lives far away,
I send it in a vial containing desiccant. This will keep the viability
high. If the shipping time will be longer than one week, I add
a cold pack to the box, which seems to help. I have been thinking
about making a shipping container that would have two compartments.
The inner middle compartment could hold the vial, and the outside
compartment could hold ice to keep the vial cooler while shipping.
If dry ice were used in the outer compartment, pollen most likely
could be shipped anywhere in the world without loss of viability.
I would like to remind everyone that all parts and products of
cycads are poisonous. This includes pollen. I have known people
who have been hand-pollinating their cycads for decades and have
never shown any obvious side effects from this, but I would still
recommend using a mask and gloves when handling pollen.
I hope this information helps everyone store pollen correctly
to insure its viability. This is especially important for those
who are mailing pollen to others. More and more people are propagating
their cycads every day, and they are also coordinating their efforts
with others by sending pollen to people who do not have male plants.
I hope this article will help everyone produce more seeds and,
eventually, more cycads.
Note: We have indicating desiccant available for sale now, but will be adding the information on this soon. E-mail me for details if you need some before I have a chance to add this to the site.
