With flamboyant, showy flowers, Spanish broom is probably the most beautiful of all the evil brooms. It is still evil, though. Don’t be fooled by the big yellow flowers with their many exuberant stamens and pretty wing-like petals.
This plant has the lean, linear look of Scotch broom but with even fewer leaves. The California Invasive Plant Council lists Spanish broom (Spartium junceum) as a species that can cause serious problems for native ecosystems. It can grow up to 15 feet tall and form dense stands that smother all other plants in the area. According the IPC, it is native to Spain, Morocco and other parts of southern Europe. It was introduced to California in 1848 as a decorative plant, and in the 1930s was planted along mountain highways in Southern California. Oops.
In Marin, it is one of the least common brooms. I saw the ones pictured here clinging to the slopes of what looks like an old rock quarry owned by the Marin Municipal Water District.
Flowers Of Marin 
Hello Flowersofmarin,
Maybe a little off topic, however, My neighbors have an amazing Spanish Broom plant. It needs to be trimmed–you cannot see around it at the busy intersection. We would like to take a few cuttings. How do we root it? Can we just plant it or do we need to put it in water and get some roots to grow first?
I look forward to your next post
I can’t recommend planting a Spanish broom since it is an invasive plant, aka weed. Despite being pretty, it is a big problem for the environment here in California and elsewhere. So I would say find a different shrub to plant, maybe even a native like monkeyflower or ceanothus. Sorry I can’t be more help –