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Peter Sharp Raising
Begonia from Seed
by Peter Sharp
Propagation is the aspect of growing
begonias which I most enjoy. Certainly
watching over precious plants as they
mature, agonizing as to whether they will
flower, finally enjoying the beauty of the
blooms and the endless variety of the
foliage as well as savoring a garden or a
shade house full of begonias, all give me
that thrill which only a true begoniac can
know. However, producing new life from
cuttings or seeds is something really
special.
I am fortunate enough
to be a horticultural volunteer at the Royal
Botanic Gardens here in Sydney, Australia
and have been such for the past 15 years, my
particular input being, quite naturally, the
care of an extensive begonia collection. We
grow them mainly in the open garden and have
some two thousand plants out of doors all
year round. Enlarging the collection is now
my present priority as we have been asked to
plant another very large garden with
begonias, and seed is the primary source of
new species for this daunting task. So I
have perforce become somewhat adept at
raising begonia from seed.
Mickey Meyer, a very
well known and much admired begonia grower,
now sadly departed, told me many years ago
that her secret for raising from seed was to
use the same mix for the seeds as she used
for pricking out and eventual potting, and
I have followed this advice with excellent
results. She explained that using the same
mix ensured that the seedlings would not
suffer much set-back when moved. How ever, I
think it wise to omit any fertilizer from
this first mix to avoid putting the
seedlings under any stress when they first
emerge.
The first and perhaps
the most important aspect of raising from
seed is to ensure that conditions are as
sterile as you can make them, for ‘damping
off' (a fungal disease) is your very worst
enemy. There are several ways to sterilize
the mix: microwaving for a few minutes,
pouring boiling water through it, or simply
leaving a flattened plastic bag of it in the
hot midday sun, will all suffice.
Two further points
before we start. Firstly, begonia seed is as
fine as finely ground pepper, so work away
from breezes, fans and sneezes, and open the
packet with extreme care. Secondly, begonia
seed needs HEAT, LIGHT and MOISTURE in order
to germinate, so neither cover the seed with
mix nor the container with other than a
cover which allows light to penetrate.
Let’s sow some seed:
1. Fill a suitable
container (I use 4” square squat pots) with
sterile potting mix, removing any large
matter (such as bark pieces, pebbles, etc.)
from the surface, and leaving a clear half
inch below the rim. Tamp it down lightly.
2. Water the mix in the
container with clean water. If your water
source is suspect, then it too may need
sterilizing. Cover with plastic or glass and
allow to stand overnight to drain. The water
remaining in the mix after draining must
last until germination occurs as watering
during the germination period is not
recommended, BUT the surface of the mix must
not be allowed to dry out during this
period. Bottom watering should be used if
watering does become necessary, being
careful not to flood the surface of the mix.
3. Next day sow the
seed, scattering it evenly and not too
thickly over the surface of the mix (a small
pinch will contain upwards of 50 seeds!).
You will doubtless work out your own way of
doing this. One method is to shake the seed
gently from a sheet of paper suitably
creased (practice a bit by trying to sow
seed onto an other sheet of paper until you
obtain an even distribution). Now, cover the
container with glass or plastic. I prefer a
suitable piece of clear plastic film secured
with a rubber band so that a good seal
results.
4. Seeds need heat of
between 70° and 75° F (21° to 25°C) to
germinate, so if you have no source of
bottom heat it is best to wait till the
weather is hot enough before seed sowing. If
you have a heat pad, then stand the
container on this in a position where it
will receive good light but not direct
sunlight. Bottom heat is often readily
available in the home - the top of the
refrigerator or the top of a floor level hot
water heater for instance. Test for heat
level before using! You will note that water
condenses on the plastic cover; simply tilt
the container to allow this water to run
free.
5. Germination will
occur in a surprisingly short time with
fresh seed, anywhere between 10 and 14 days,
but this may take longer. Some seed can take
up to two months before coming good, so be
patient! The first indication is a slight
green bloom on the surface of the mix, but
the small seed lings will soon look more
like real plants!
6. It’s about here that
I disagree with the experts! They tell us to
gradually lift the cover from the pot over a
period of a week or more, commencing some 10
days after germination, their reason being
‘to harden off the seedlings’. I maintain
that begonias are tough plants and I have
had no problems with lifting the covers
completely about a week or 10 days after
germination I then take the pots off bottom
heat onto my growing benches. HOWEVER, this
should not be done if local overnight
temperatures are likely to drop below about
50°F (10°C). Do not leave the uncovered
containers on bottom heat as the mix will
very quickly dry out, more quickly than you
think, and you will lose your seedlings!
Once again, wait till warm weather before
seed sowing, unless of course you are
fortunate enough to have a heated
greenhouse.
7. At this stage I also
commence feeding the seedlings, using a good
water soluble fertilizer in a hand mister.
Not much at first, but gradually increasing
both the amount and frequency, and again
contrary to the experts, I mix the
fertilizer according to manufacturer’s
recommendation, not the half or quarter
strength the experts often say!
8. The seedlings will
stay the same for a week or two while the
root systems develop, and then they will
suddenly start to grow, and when this
happens they will very soon put out their
first true leaves. This is the stage of
growth when it is necessary to prick out the
seedlings into their next container.
Certainly they are still very small plants,
but that’s the thing to do so don’t be
worried!
9. These small
seedlings need company in their next
container, so don’t be tempted to plant them
singly in small pots—they will more than
likely die. Plant them no more than one inch
apart in a suitable container. Usually you
will have a lot of seedlings, so find a
seedling tray (we call them nursery
‘flats’), fill it with mix which this time
contains a ration of controlled release
fertilizer, dibble holes an inch apart, and
gently move the seedlings from their seed
bed. It takes a little practice to untangle
them if you sowed too many seeds! It is
beneficial to plant them a little deeper in
these trays than they were in the seed
trays. Weekly fertilizing with a nitrogen
rich fertilizer is now required. In no time
at all your seedlings will be ready for
potting up.
Now that wasn’t so very
hard, was it? And you have perhaps
discovered a new aspect to begonia growing,
and a fascinating way to increase your
collection of species.
Peter’s growing
collection includes the following species
grown from seeds:
B. barkeri, B.
carolineifolia, B. chivatoa, B. fusca, B.
heracleifolia, B. mariti, B. nelumbiifolia,
B. sericoneura, & B. wallichiana.
Peter Sharp lives in
New South Wales, Australia
Further reading: Growing Begonias
by Peter Sharp. Kangaroo Press NSW 1998
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