Propagating orchids using back bulbs

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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 illustrated below.

Carefully examine the plant and establish which bulbs you will be leaving on the main plant and which bulbs you can remove.

 2000 Orchid-Guide.com

Here the plant has 2 good leading growths each with sufficient back bulbs to remain flowering size once the spare bulbs are removed.

 2000 Orchid-Guide.com

 2000 Orchid-Guide.com

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 scissors slice 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.

 2000 Orchid-Guide.com

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. 

 2000 Orchid-Guide.com

 2000 Orchid-Guide.com

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.

 2000 Orchid-Guide.com

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

 2000 Orchid-Guide.com

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 pots water 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 clear bag.
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.

Congratulations - you have now produced your first orchids using the back bulb method.

 

 2001 Orchid-Guide.com

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.

Bealarra Tahoma Glacier Green back bulb 07 Aug 2001

Update 07 August 2001

As you can see, this back bulb is growing away very nicely and is forming it's first pseudobulb!

Odontoglossum back bulb propagation

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.

Coelogyne massangeana back bulb propagation

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.

 

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