As the world gen script for the main world did not spawn any Silverwood trees, or even many Greatwoods and Witchwood trees, there should be a bot at the spawn that sells saplings at 100 MyM for 2 or something like that. I've searched both Farmworld and the Main World and found only a handful of Silverwoods and even less Witchwoods. I know they should be rare, but in the past, they were never that rare.
FTB changed a lot of configs to make stuff more rare not only in thaumcraft. I think it is wanted like it is by them. Are they realy that rare that we need to sell them ?
Go hunting for a Silverwood tree and tell me how long it takes you to find one. Then see if you get at least one sapling if you cut it down. I've only found one magical forest, and that was in Farmworld and I've nearly emptied it of Silverwoods (I've found about 3 stacks of wood so far). I can imagine other players are having the same difficulty. And it is not just Silverwoods. Greatwoods and even Ars Magica's Witchwood are unusually hard to find. Selling them for a fee (maybe even 200 MyM for one sapling) can save players from the time wasted searching from border to border in both worlds like I had to. I believe Farmworld is currently generated using the old gen code. When it is regenerated, it will most likely have no magical forests in it.
You must be in all the right spots then. I bounced back and forth, from corner to corner, looking for them. Only found one MF with some Silverwoods in them. Took a few days to find. And remember, when the farmworld is reset, there will be a very slim chance of silverwoods spawning if the main world is a good example.
10 mins in the farmworld but i've found only 1 sapling so far[drop rate so loooow] greatwoods & witchtrees are not so rare (easily found in less than 1 min either world it was) but i second the silverwood sap selling since that mother-*beeep* taint spreads everywhere @ an alarming state