It had roots, and it bloomed last fall, although not a flush. I don't think the nematodes actually eat away the roots completely. However, the plant struggles and eventually dies. This one has been potted the 2 (3?) years I've had it, so I think it's probably been sick for quite awhile. It was the first brug I ever had, and it's never done well for me. Since I don't know much about brugs, I thought it was just me.
I think nematodes are strictly soil-borne, so yeah, they do move through the soil and infect other plants. And yes, I do hear that marigolds help. Some other suggestions I've gotten are adding molasses, using beneficial nematodes, and giving the plant itself a hot water treatment. That last one doesn't help protect other in-ground plants, though.
