To the best of my knowledge, thistle seed for feeders has been
sterilized so that it will not germinate. I read this somewhere
once, and my experience from feeding thistle seed at my feeder
all last winter was that no baby thistles appeared nearby. Not
so for sunflower seed, though. Every year I get volunteers in my
lawn.

--
Barbara Combs obie '70
Eugene, OR
bcombs at ednet1.osl.or.gov