Is it safe to plant Cytisus scoparius ‘Moonlight’ here on Whidbey Island? I know that Scotch broom is thought to be invasive, but I wonder if maybe this variety is less of a problem.
Some sources (such as the State of Oregon’s noxious weed control board) have said that “sterile cultivars” of Cytisus scoparius are exempt from regulations governing noxious weeds. However, the Center for Urban Horticulture’s Professor Sarah Reichard, an expert on invasive species, says the following:
“The ‘sterile cultivar’ issue is huge worldwide. The reality is that sterile cultivars depend on the type of sterility: there are many reasons a plant might be sterile. Only a few of them can be considered to be stable under varying environmental conditions.
Regardless of what is done in Oregon, in Washington it is illegal to sell or grow any cultivars of Cytisus scoparius. Moonlight is less aggressive, but I have definitely seen it seeding out. But it does not matter how aggressive it is: it is still on the quarantine list in this state because that is the way the state law is worded. Island County may not have it on their high profile noxious weed list because it is only a B non-designate there because it is widespread. But our noxious weed (control) and our quarantine lists are two different things in this state and it is quarantined here.”
For future reference, here are links to Washington State Plant Quarantine and Noxious Weed lists.