I have three spartium junceum (Spanish broom). One has been growing in my Vancouver Island garden for several years. There is a lot of dieback after the winter, often two-thirds or more of the plant. Last year a couple of seedlings sprouted for the first time, so I now have three bushes. The fragrance is divine. I read that in some places, this is considered a noxious plant. I want to be a good steward of the environment: should I remove all three and put them in the trash?
We have an invasive Cytisus scoparius (a relative to the Spartium junceum) spreading here in Estonia, under the pine forest in the territory of former Soviet military base near Tallinn. This plant was most possibly brought here by Soviet soldiers from the Caspian sea area ca 80 years ago. It does not spread quickly over long distances and is mostly confined in the military polygon (only few small outbreaks to the neighbourhood have happened during 80 years), but seem to be fully naturalised and each year its shrubberies are expanding slowly locally from seeds (birds or wild animals does not spread those seeds considerably, outbreaks to the neighbourhood have been most possibly antropogenic). When blooming, they are rather decorative with their abundant large yellow flowers, but the blooming period is rather short. No significant frost damage has limited its expansion during last 10 years in the generally Zone 5 winter climate.
With the trends in climate change, it will become likely more of a problem in the future. It likes a more Mediterranean climate, as is projected (though perhaps with more winter rain).