Published: 30 January 2013
Orchid Propagation
Chris Allen goes behind the scenes at Burnham Nurseries to learn about the fascinating process of Orchid propagation.

A new and fascinating world opened when I discovered how the propagation of orchids from seed is carried out.
 
On my second visit to Burnham Nurseries in Devon I was shown around their new seed propagation laboratory and growth room where we followed the story from pollination of the mother plants to saleable plant stock.

The production of species orchids at Burnham Nurseries starts in the glasshouse with the hand pollination of the flowers on selected mother plants. Careful labelling is essential at this stage to ensure the provenance of future offspring is accurate. After successful pollination and fertilisation, the formation of seed pods will take place. It is from these ripened pods that the seed will be extracted. The developing pods are inspected regularly to observe any signs of splitting from the base along the longitudinal joint. Pods are usually still green at this point so careful observation is required to ensure harvesting is carried out before seed is lost. This process can take many months.

A labelled seed pod nears harvesting time

Sterile Conditions

 

The Autoclave machine
From this point the seeds will be worked on and grown in the new laboratory and growth room at Burnham Nurseries. The seed is extracted by hand with other organic debris being carefully removed with tweezers to reduce the risk of future contamination. It is from this point onwards in the propagation process that maintaining aseptic conditions are critical.

All equipment is sterilised in an electric autoclave machine with all plant material being handled only in a laminar air flow cabinet. Hand held tools are routinely sterilised with a naked flame to reduce the risk of cross contamination of plant material.

The cleaned seed is sown on a layer of clear, sterile agar jelly within a sealed class flask. These are then taken to the adjacent growth room and placed onto shelves where they will remain until they have germinated. The orchid seeds do not contain any nutrient to promote growth once germination and formation of the protocorms begins, for this reason the agar jelly replicates conditions as closely as possible to those found in the wild by containing sufficient nutrients to promote this early growth stage.

The growth room is a white painted room with layers of white shelves, above each there are banks of florescent grow-light tubes controlled to be twelve hours on and twelve hours off. The temperature is controlled to maintain a minimum of 12 to 14c.

The laminar air flow cabinet is essential when handling plant material

After many months some species will have grown sufficiently in size to allow the careful ‘transflasking’ process to be carried out. This is the equivalent of pricking out conventional seedlings into compost. These tiny orchid plants in the Burnham Nurseries growth room still require strict ascetic conditions being maintained during this delicate operation. The agar jelly in the flasks is coloured black, this indicates that charcoal and banana extract has been added to provide a high potassium feed to stimulate new growth of the young orchid plants. Continuous monitoring of the flasks is essential to ensure that no contamination is present as this would cause rapid spread of diseases within a flask. Routine observation is also required for signs of strong root and leaf growth which indicates the young plants are nearing the time for moving on to the next phase.

Sealed glass flasks in the Growth Room

Plant Growth

 

An amazing aspect of this growth stage is that certain species will be kept in the same, unopened sealed flasks within the growth room for up to two years before they have made sufficient growth to start the next stage of the production cycle. The microclimate within the flask and the management of the growth room enable this to take place.
 
When each flask of plants is considered ready for the next stage they are gradually hardened off to acclimatise the plants, then they are removed from the flask and separated and washed to remove the agar jelly prior to potting on into cell trays using a perlite, bark and a small percentage of fine peat mix. The planted cell trays are then placed on wire mesh benches within the glasshouse. Free drainage with high humidity and warmth are essential to promote new growth on these young plants.

Replicating Nature

 

In conversation with nursery owner Sara Rittershausen the importance of replicating the growing conditions found in nature is critical in these early stages after the plants have come from the growth room. It is at this stage that the young plants come out from the sterile conditions for the first time. This point raises the interesting fact that orchids growing in the wild produce vast quantities of seeds that are distributed within the surrounding area, however because orchid seed has no nutrient ‘built in’ it is essential seeds must fall where there is sufficient moisture and warmth and the right sort of mycorrhizal fungi to promote root growth; without this the seeds will not live. 
 
This dependency on specific species of mycorrhizal fungi explains partly why certain orchids are found growing naturally in clusters only where the right mycorrhizal fungi has also colonised. At the nursery the use of glass flasks with agar jelly in growth rooms is replicating the natural conditions - the difference is that in a commercial nursery the quantities of seed are infinitely smaller than in wild populations so every seed must perform compared to the wild locations where the natural wastage is huge due to lack of suitable conditions.

Sara Rittershausen inspecting recently planted cell trays

The Rittershausen family have been hybridising and propagating orchid species from seed for the past sixty years, it is their specialist work with orchids that has produced some of the most beautiful and exquisite flowers on earth. 
 
To see many orchid plants visit the nursery to view their collection known as Orchid Paradise or book a place on one of the many orchid workshops or master classes. For more information see the website: www.orchids.uk.com

Orchid Master Classes

 
You will also find details for the 2013 Orchid Master classes run at the Burnham Nurseries site in conjunction with the RHS. The Beginners classes are February 24th and September 1st with two follow on classes on March 16th and another on October 6th.
Reported by Chris Allen  
   
 

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