Back Bulb Propagation of Orchids
|Propagation by back
bulb is an excellent way of increasing your stock of a particular variety
or cultivar, it is however a slow method if flowering sized plants are
required. Often used with Cymbidiums it will take between 3 to 4 years to
obtain a flowering size plant from a single back bulb. The process does
have the advantage though of being straight forward.
This process involves the complete removal of
the back bulbs either previously flowered or unflowered and so is quite a
shock to the parent plant, the back bulbs are the plants store of food and
water for use in times of drought or a bad season. This is unlikely to
occur in cultivation as we tend them all year round giving them the
optimum conditions for growth and so really the back bulbs can be removed
without too many problems provided a few basic rules are adhered to.
ALWAYS make sure that the plant you are using for propagation will be left
with at least
two back bulbs (or back growths) and a new growth, this will keep it at
flowering size and it will be capable of flowering in the following
season. Only remove bulbs from plants which are healthy and strong, a weak
plant will probably not survive the shock of having its older food stores
removed and it's roots trimmed. Keep both the 'cutting' and the parent in
a higher humidity until new growth is seen.
|Here we are using a Beallara which has become too large for it's pot and is
need of repotting. Any new roots and bulbs the plant produces
outside the rim will not come in
to contact with the compost and so feeding will also be a problem.
We will be removing the bulbs as
Carefully examine the plant and
establish which bulbs you will be leaving on the main plant and which
bulbs you can remove.
Here the plant has 2 good leading growths
each with sufficient back bulbs to remain flowering size once the spare
bulbs are removed.
Remove the plant from it's pot and
carefully remove the old compost and dead roots. - see opposite
With a sharp preferably sterile knife or
behind each flowering size division cutting through the tough
rhizome which connects the bulbs together.
You can now pot up the leading growths as
described in the Division section.
We are now left with some older back bulbs
which in this instance are leafless. See opposite
The clump of bulbs can now be separated in to
individual bulbs by slicing carefully through the rhizome which connects the
bulbs to each other.
We now have individual bulbs which can now be
prepared for propagation.
Remove any dead roots from the bulbs as these
can cause rotting and the bulb may rot before any growth can start. Wash
the bulbs in a 5 percent solution of either household bleach or Milton Fluid,
this will kill off any bacteria which may be present. Take care not to
damage the dormant buds (eyes) which are at the base of the bulb.
If using the plastic bag method place the
bulbs in individual bags to avoid rotting problems, if one bulb starts to
rot then this will ensure it doesn't spread to the other bulbs also make
sure you put some small holes in each bag to allow the air to
circulate. Put a label in each bag with the plants name and the date
of the propagation.
There are now two
choices open to you, you can either place the cleaned bulbs individually
in to clear plastic bags of moist (not wet!) compost or sphagnum moss and hang them
in the highest and warmest part of the greenhouse (see opposite) or you can place the
bulbs in individual pots of fine grade compost. see below
If you are using the pot method use a bark
mix is which is fine grade, this will hold the moisture and yet remain
open enough to prevent the bulbs sitting in wet compost. Place the bulbs
in the pot by just pushing the very base of the bulb in to the mixture.
Once all your bulbs are in their
them in and place in a warm position out of direct sun and in a
place that they will not be disturbed. Put a label in each tray with the
plants name and the date of the propagation.
After a period of 12 - 16 weeks you
should see small shoots appearing from the base of each bulb. If any bulbs
show signs of rotting - REMOVE THEM IMMEDIATELY!
|Both of the above methods work well but
take differing levels of looking after, the plastic bag method takes less
as they need not be disturbed until signs of roots are seen through the
Once you have seen the bulbs have roots and/or
shoots it is time to pot them on.
You can either place them in to individual
pots or in to communal trays. In either case us a medium grade compost this
time and again label each pot or tray so you know what it is you're growing.
By the following spring the plants will be
large enough to put in to larger pots which should have sufficient room for
two years (seasons) growth, after this two years growth they should be
either flowering size or near flowering size.
you have now produced your first orchids using the back bulb method.
Update 08 April 2001
Here's the first signs of growth from the back bulbs
from above, this first stage has taken 4 months to the day from when
the bulbs were potted on.
Update 07 August 2001
As you can see, this back bulb is growing away very nicely and is
forming it's first pseudobulb!
Update 15 October 2001
Here's the back bulb that was kept in the plastic
bag. As soon as the sprouts are an inch high its time to burst the bag
and allow atmosphere to enter, this will harden the growths and help
prevent fungal infections. This bulb has produced two nice sprouts
which we will be potting on soon.
10 September 2001
This is a back bulb from Coelogyne massangeana which
was given the 'bag' treatment back in May 2001.
As you can see it's doing well and is on the way to
becoming a flowering size plant in around 3 years or less.