I'm finding conflicting information (online) about this plant... I wild collected the seed a couple of years ago, and in my garden, it seems to spread less than rudbeckia hirta. Interesting that it's considered a noxious weed in so many places.
The seed is very small (can blow a long way), and can stay dormant in the soil for a long time, so even if it doesn't appear to be spreading, it might still be doing so.
You know.... If your answer had anything to do with it... we'd be seeing stuff like lambsquarter Chenopodium sp. on the list.... 80,000 seeds on one plant... c'mon! Clearly the problem has more to do with this plant being poisonous, and it colonizing marginal dryland, than the size of the seeds and the length of time for viability...
I am an admirer of the echium family including E. vulgare which I admire for its true blue flowers and which I moved into my garden about 7yrs ago. Mine is a very dry area in zone 4. I have had no problems with rampant spreading and this plant has not showed up in my neighbours' fields each starting 300 to 400 ft away. The drawback to this plant for me are those fine hairs once the plant has dried out at the end of summer -- which cause mechanical, not chemical irritation -- and one needs gloves to pull the finished plant out. Rather surprised by the post claiming toxicity for this plant, I too did a search and the Government of Canada site specifically states that 'there is no information in the literature" causing any poisoning to livestock or human by Echium vulgare. Is the claimant, Stone, possibly confusing E. vulgare with E. lycopsis? In fact the Wikipedia site reports that E. vulgare is grown as an oilseed crop. I say bravo to using a beautiful plant, albeit considered a weed, in a garden setting. The bees also like it not surprisingly as it is in the borage family. True, they do like borage somewhat better. To Michael F. also try Echium russicum- absolutely stunning (pink) solid spike of spring blooms.
