Home | Contact

Growing orchids from seed

Is growing from seed worth the wait?
Orchid seed is like no other flowering plant seed in a number of ways.
Firstly, seeds have a built in food store that gives the developing plant enough food to produce a few roots and a couple of leaves. This built in food store is sufficient to sustain the plant until the leaves are large enough to provide further food by photosynthesis (the plants ability to convert sunlight in to growth). Orchids however don't have this food source built in and are more closely matched to fern spores than flowering plan seed.

 2000 Orchid-Guide.com  

Tiny orchid seed from a Dactylorhiza (UK species)

This is where the second main difference is observed, symbiosis. Many orchid seed relies on another organism to provide it's first food for growth, this comes in the form of a fungal mycorrhiza. Although these are fungi like mushrooms and toadstools they don't have any real substance as they exist in the soil and are not evident without the use of a microscope. The mycorrhiza is the root system of fungi which enters the cells of the emerging embryo and supplies it with basic sugars which enables it to grow, some orchids are so dependant on this system that they have become parasitic on their specific fungi and rely entirely upon it for the food supply throughout their life. 

There are two ways of growing orchid from seed, symbiotic and asymbiotic. Sowing seed using the symbiotic method can be as simple as scattering the fresh seed on to the surface of the plant from which it came, this will with luck become infected by the mycorrhiza that is present in the 'mother plant' pot. This seed will hopefully begin to show signs of growth after about 12 months. Seed which is sown asymbiotic has to be sterilized before it is sown to remove any unwanted diseases or bacteria which would ruin any attempts to germinate the seed. Once the seed has been sterilized it is then sown on to the surface of a special growing media containing N, P, K and trace elements plus some form of sugar. The developing seed eventually forms protocorms which are the developing orchid embryos. Once you have enough protocorms you will need to divide them in to smaller clumps and re plant them (re flask) on to fresh growing media, again all under sterile conditions. After approximately 12 months the developing plants should have filled their sterile containers and can be planted out in the greenhouse either in individual pots or in communal trays.

The process of sowing to flowering can take up to 4 years or more (depending on type) to obtain flowering size plants.

Growing Medium

Growing media formulations specifically made for orchid  seed sowing can be purchased in kit form. They are available in a wide variety of types as each orchid genera has specific requirements in terms of what nutrients and hormones are required and in what combinations. The kits purchased may or may not contain some or all of the following ingredients:

  • Macronutrients:  calcium (Ca),  magnesium (M), nitrogen (N), phosphorous (P), potassium (K) and sulphur (S). 
  • Micronutrients (trace elements): boron (B), cobalt (Co), copper (Cu), iodine (I), iron (Fe), manganese (Mn), molybdenum (Mo) and zinc (Zn).
  • Vitamins: nicotinic acid, pyridoxine (B6), riboflavin and thiamine (B1)  
  • A food source: Usually in the form of glucose, sucrose and myo-inositol
  • Growth Regulators (phytohormones)*: Both auxins (IAA, NAA) and cytokinins ( BA). 
  • Solidifying Agent: The most commonly used is agar  

* A mixture which contains all of the ingredients except the growth regulators is know as a 'base mixture' 

Once you have mixed your growing medium according to the pack instructions it must be placed in to some kind of glass vessel, usually these glass vessels are either conical flasks or some other similar glass container such as honey jars which must be sterilized by autoclaving. A house hold pressure cooker will suffice for this. Your containers containing 1/2 inch of growing media need 'cooking' for between 10 and 14 minutes to sterilize them. If you are using screw on lids then you will need to put these on and then unscrew them half a turn, this will ensure your vessels don't break under the pressure whilst avoiding water getting in to the containers.

After the initial 'cooking' time the jars or flasks should be allowed to stand in the pressure cooker until cool enough for the pan lid to be removed but before it gets too cool. As soon as it is safe to remove the pressure cooker lid you should open it and immediately fully screw on the lids of the jars without removing them from the cooker. As they cool they will form a vacuum and the contents will be sterile. These jars can be made in advance and kept in your fridge until needed.

Can I sow seeds at home?

By far the most difficult aspect of the whole process is keeping everything absolutely sterile.

A method that is commonly used with some success is to use a large wide rimmed cooking pot half filled with water, this is brought up to the boil to give off a wide plume of steam vapor. Inside this veil of steam the atmosphere is sterile and so where we mention a Laminar Flow Hood you can substitute your wide rimmed cooking pot.

The steps

Firstly prepare some jars of growing media (see above) and place them beside the cooking pot which should be boiling

Seed Sterilisation
 2000 Orchid-Guide.com

There are two commonly adopted techniques when it comes to sowing orchid seed, the green pod method and the dry pod method. Seed which comes from a green pod is generally sterile as the insides of the pod haven't come in to contact with the atmosphere and so should not be contaminated.

Seed which comes from a dry pod however will have been exposed to the atmosphere and may be contaminated and so will need to be re sterilised before it can be used.

If you are using the green pod method you need to scrub the outside of the green pod with a 5% solution of bleach and then place the whole pod in a 5% solution of bleach for 5 to 10 minutes. 

If you are using the dry pod method then you will need to remove the seed from the pod and place it in to a test tube containing a 5% solution of bleach for 5 minutes to eliminate any bacteria etc. see left

Flasking it up 

Now that your seed is sterile you will need to rinse it several times in sterile de-ionized water to remove the bleach solution. This has to be done within the plume of steam rising from your boiling pan. Carefully empty the bleach solution from the test tube making sure you don't pour out your seeds then replace it with the sterile water and give it a good shake. Repeat the process two more times. ALL WITHIN THE STEAM PLUME.
Using your other hand take one of your ready prepared flasks and bring it in to the steam plume, carefully remove the lid of the jar and using a sterilised instrument (here a spoon handle) place SOME the sterile seed (with as little water as possible). 

 2000 Orchid-Guide.com

Make sure that you don't touch the inside of the lid you have removed - see left - the inside of the lid will then remain sterile.

Make sure that you don't put too many seed in the jars as they will become overcrowded. If in doubt UNDER SOW Replace the lid of the jar.

 

If you were using the green pod method you should take the pod over to the pan and split the pod open whilst working within the steam plume. Bring over a prepared jar of growing media and empty SOME of the seed in to it. Don't put too many seeds in to any one container as they will be overcrowded. 
 2000 Orchid-Guide.com

The jar above has been contaminated and fungal growth has taken over, this contamination only took 2 days to manifests itself and is caused by a lack of sterility.

Replace the lid on the jar containing the growing media that is now sown with your orchid seed.

Make sure that the whole of the process is done WITHIN the steam rising from the pan, this is sterile.

In both cases the jars of seed should be placed in a warm and bright position but not in direct sun as they will overheat and die.

 

 2000 Orchid-Guide.com

Protocorms

After 4 to 12 weeks you should see some growth activity and the surface of the growing media should be covered by tiny green balls, these are called protocorms and are the developing orchid plant embryos. Depending on how many seed you originally sowed and the fertility of the seed, you may have thousands of green protocorms or just a few. If you have thousands then you will need to divide them and re flask them using the same process as described above for flasking. If this is the case then you need to remove a few small clumps of protocorms using a sterilised tool such as tweezers, you will need to sterilise the tweezers in a solution of  5% bleach be fore using them and then re-flask the protocorms as if they were seed, THEY DON'T NEED STERILISING THOUGH! 

Growing on

After a further 12 to 26 weeks your protocorms should have developed in to tiny orchid plants which can be re-flasked in to individual flasks (using the method above) or if large enough they can be potted in to communal pots containing a seedling orchid compost mix. They will need to be kept warm and humid for the first 4 to 6 weeks and can be placed in a propagator with a lid. The lid should be gradually lifted each week to allow more and more air to enter the propagator, this will hardened the young plants off ready for being placed in the main greenhouse.

You can expect plants grown from seed to take up to 4 years to flower (depending on genus)

 

Here's some useful equipment you may need with summer on the horizon
Thermometers | Thermostats | Humidity Gauges

Home | Contact