The Alien Plant Working Group of the Plant Conservation Alliance, located in Washington, D.C., offers a November 29, 2000 fact sheet entitled "English Ivy (Hedera helix)," written by Jil M. Swearingen.

... English ivy ( Hedera helix ' Baltica ' , H. helix ' Pittsburgh ' , H. helix ' Star ' , H. helix ' California ' , and H. hibernica ) have been declared Class C noxious weeds in western Washington and Class B noxious weeds in western ...

... Stanley Park's centennial celebrations, the Stanley Park Ecology Society (SPES) was its original name was the ... English holly trees fellout of favour. It's easy to see why. They don't belong in Stanley Park. Cultivated holly ...

... English ivy cultivars , only four have been identified as invasive in the Pacific Northwest : Hedera helix ' Baltica ... Stanley Park , where ivy stands accused of having a significant negative impact on the diversity and ...