Growing orchids from seed
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.
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 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:
* 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.
Firstly prepare some jars of growing media (see above) and place them beside the cooking pot which should be boiling
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.
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.
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!
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)