The seeds of the weed plants are carried around by the wind. It's hard to stop them completely, by you can reduce the weeds by keeping the area around your garden clean (if there is a chance to do so, of course).
I am sorry for late reply, anyway I would reply here for getting rid of weeds from plants. You need to place the plant or plants away that are affected and use some medicine to kill these weeds. The earliest you clean, more easier to restore your plants health else they may die.
I wil look some of the medicines for these weeds in the coming days to put in our store. Can you post an image of your plant that affected from weeds.
It is nice to hear about your experience in gardening than me, however I too tried in these weeds removal, but it takes some time from us. As per the OP please use your time to remove them or hire someone who can maintain it in removing Weeds.