Hablitzia as a weed!
While researching Hablitzia tamnoides for my book Around the World in 80 plants (2014) I found the following simple entry in a 19^th century encyclopedia of ornamental plants:
The author was clearly not impressed…..
Further Frederik Christian Schübeler (1815-1892) who was professor of botany and manager of the Oslo botanical garden at Toyen in Oslo from 1866-92 also noted from northern Norway that
“At Maalselvdalens Vicarage (69 deg. 10 min. N), where it also grows very well, it reaches 8 feet (2.5m) and doesn’t only give mature seeds, but spreads even in the garden as a weed.”
I found this difficult to believe and thought initially that it had been confused with good king Henry (Chenopodium bonus-henricus) which can be very weedy in a garden. I only had one plant at the time and I struggled to get more than a couple of seeds from it. Introducing a second plant, suddenly there was a lot of seed and seedlings appeared around the mother plants.
Nowadays it appears in many parts of the cultivated parts of my garden spread by the low friction seeds blowing around on ice in the winter and through my compost. Small plants often turn up as a weed in pot plants indoors which have been fed with compost. This is a plant which germinated in a pot with a bay tree (Laurus nobilis) some years ago. When the bay died, I let the Hablitzia grow on and it now uses the bay as a climbing frame!

Nevertheless, Hablitzia seems to depend on naked earth to establish itself here and there are no reports of it escaping into nature approaching 150 years after its introduction as a garden plant here.
Yesterday, I was weeding Hablitzia from newly emerged carrot seedlings!