I just checked my vine, it was fully grown but there was no pick option...... And when I tried to dig it up it didn't fight. But then I talked to the farmer and he said I hadn't gotten to the root of the problem yet and he gave me another seed. Hmmmm......
Maybe when your vines grows up you can kill it, thus giving you slayer exp. Then you can get another seed for free and plant it, giving you farming exp, etc. Its just speculation right now cause my vine's still growing.
I would like to point out an error in your article. You can in fact use the Moonclan bank without the Seal of Passage. Just right click and select "Use Quickly". Or right click and select "Bank Bird Eye's Jack(or whatever his name is)". However, this is one of the best and most well thought out articles I've seen in....ever! =D>