Orchid seeds are tiny and have no stockpiled nutrients to help them start growing. This condition is probably an adaptation to allow production of huge numbers of seeds at low cost, and for allowing them be spread easily by wind. (In case you never noticed, avocados go to the other extreme, much to the consternation of epicures.) The vast majority of seeds end up in an inhospitable place and never germinate - this is true for many plants but it is probably more extreme for orchids. Even when an orchid seed lands in a prime spot, for example lodged in a crevice in damp bark with the right sun exposure and at the right altitude, its trials are not over. There the seed needs to encounter a symbiotic fungus that will provide sugar to get growth started (later the orchid will reciprocate but as far as I have read this street starts off one-way). The seeds need various other nutrients just like all plants, but it is mostly sugar that is provided by the fungus (or other small organic molecules in some cases) - sufficient minerals leach into the rainwater after it falls. The seeds do not carry the fungus with them - perhaps the fungi are widespread enough to make it unnecessary or perhaps it is hard to evolve a fungus-carrying seed. Once the tiny orchid plant starts photosynthesis it can fix carbon from the air, but it can't get to that point on its own.
In the early days of orchid horticulture, before all this was known, attempts to grow orchid seeds were miserable failures. The seeds just sat there or grew mold, quietly mocking the botanists and Victorian millionaires. For a few orchids, it was noticed that seed would sprout if it was just next to the parent plant, which provided an early tip that something else was necessary - something associated with the parent plant. In 1909, Bernard discovered that germinating orchid seeds depend on a mycorhizal fungus (more abundant near the parent plant), but this discovery did little to improve the practical problem for horticulturists. Finally, in 1922 Knudson showed that many orchid seeds would germinate on a defined medium containing nothing but a few salts and sugar. The orchids don't need the fungus - they only need the sugar the fungus provides! This was the breakthrough for humans trying to raise orchids from seed, though precise definition of the optimal salts and organic compounds for different types of orchids is still being worked out.
Since Knudson, orchid seed is grown aseptically with only appropriate salts and sugars (and light and air) provided, typically with agar to provide a gel base. The method is common enough that you can find many how-to guides for the process and you can even buy prepared commercial agar medium to get started. The process is still a bit involved because bacteria and (bad) fungi also love this medium and will kill the slow-growing orchid embryo, so you have get rid of the bad guys. With care though, apparently you can do this in your kitchen with only a pressure cooker for sterilizing media and minimal laboratory equipment such as glass flasks.
Development from seed to adult flowering plant is still agonizingly slow, but at least it is routine. As you know if you grow orchids yourself, pretty much everything about orchids happens in slow motion. Some orchids take 10 years to go from seed to flowering plant, about the same as small trees. Some grow one new leaf per year. No bean or basil or avocado seedlings in the orchid world! Nearly all orchids are highly adapted to very low nutrient conditions, so only slow growth works. Even most terrestrial orchids occur in low nutrient environments and follow the same rule. Some types of orchids make impressively rapid growth at the start of their wet season (e.g. Catasetum and relatives), but this is deceptive - they are converting nutrients from their fat pseudobulbs from the previous year, painstakingly acquired over the growing season. Their averaged growth rate is much less impressive. I suspect this slow growth is part of the magic of orchids - how can a plant that hardly seems to do anything at all from week to week produce these amazing flowers!? That will be another post - there is an answer.
As ye sow, so shall ye reap. But be sure to add sugar.
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