Growing orchids from seed
Most seeds have a small packed lunch included, which will get them as far as the first root and first shoot and leaf, then photosynthesis will take over and the plant can feed itself. The orchid has no food store, it is just an embryo with a seed coat and it has to meet a fungal partner in the soil to supply its food. The fungal hyphae penetrates the seed coat and the orchid embryo steals food from the fungus for those first few months of life, before it puts up a green shoot and photosynthesis can begin. There are some orchids such as the Birdsnest orchid and the elusive Ghost orchid which have dispensed with the green leaves and photosynthesis altogether. They spend their whole lifecycle sponging on the fungal partner. But the fungus is probably a part of a huge underground network of mycorrhizal fungi and roots, and the food being stolen by the orchid may have been be produced by a nearby tree. Very little is known about these intricate underground connections.
But why does the orchid make life so difficult for itself? There must be an evolutionary advantage in all this because the orchid family worldwide is huge, infinitely varied and highly successful. The strategy allows orchid seed to be produced in very large numbers and to be very small and light. Some seed is just like fine brown dust and when it is released it can float away on the slightest air current and travel many miles. This allows orchids to be opportunists and primary colonisers. Many of them live in very poor soil on dunes, gravel pits, slag heaps and in tropical parts of the world many species live on trees as epiphytes with no soil at all. So their fungal partners allow them to live and thrive where other plants cannot.
Propagation of orchids usually starts off in sterile conditions in the lab. We have some symbiotic fungus in captivity and can use this to grow a number of the more common species on petri dishes of agar and porridge oats. But there are many species for which we do not have a fungal partner and these can be grown on a more complex agar medium containing all the nutrients they need. They often like additional snacks added to the media, such as coconut water, pineapple juice, potato and turnip. Germination takes place in the dark and can take a few weeks in some species, in others it takes many months. The embryo then grows into a protocorm, which is a ball of cells with root hairs, this develops to produce the first root and shoot. They can then be moved into the light and start to photosynthesise.
When they get too big for a petri dish they go into honey jars and grow into a small plant. Once they have a good root system they can go outside into pots of our compost mix.
Our native terrestrial orchids do best in a well drained compost mix with lots of grit and perlite. Even the marsh orchids grow better with some airy compost around the roots, particularly in the winter when they can die if they become very cold and waterlogged.
Once they have grown to a good size in a 9cm pot they are ready to be planted out in the soil and if the position is chosen with care, the survival rate is very good. For the more common species the fungal partner will probably exist in the soil and the orchids can self-seed successfully. Seed to flowering can take 3 years but may take 5 or more years depending on the species and the local conditions.