Real name: Hedera helix. Also known as common ivy, English ivy, European ivy, or just ivy. There is quite a variety of strains as far as adding yellow and white accents to the leaves. Ivy genetics is, so as to speak, a tangled tale. The basic diploid number of chromosomes is 48, while some are tetraploid with 96, and others hexaploid with 144 and octaploid with 192 chromosomes. There is some disagreement about the number of species of Hedera: the most common estimates are 12 and 15. There are three generally agreed subspecies of Hedera helix:
H. h. helix – from central, northern and western Europe; usually has no rhizomes; features purple-black ripe fruit
H. h. poetarum – from southeast Europe and Turkey; usually has no rhizomes; features orange-yellow ripe fruit
H. h. rhizomatifera – from southeast Spain; has rhizomes; features purple-black ripe fruit
Note that the closely related species Hedera canariensis and Hedera hibernica are also often treated as subspecies of H. helix although they differ in chromosome number. This makes hybridization difficult.
Note that if one has students with an allergy to carrots (well, strictly, a type IV hypersensitivity), ivy usually has falcarinol. That would be unfortunate as ivy was noted by NASA as effective at removing benzene, toluene, formaldehyde, xylene and trichloroethylene.
Oregonians take note: sale or import is ILLEGAL
I believe ALL the various Hedera species are defined in California as invasive. In fairness, from the point of view of a redwood tree or a spotted owl, Homo sapiens is an invasive pest that devastates environments and is seemingly impossible to eradicate. Other hominids in California: zero. Other primates in California: zero. Other large mammals: elephants: zero; camels: zero; horses (9,000 wild; 700,000 domesticated – down from 10 times that number a century ago); wolves (I believe the Shasta pack is gone and only the Lassen pack MIGHT survive – I doubt they have ten animals); mountain lions (hard to tell – maybe 4,000 to 6,000); black bears (probably between 10,000 and 15,000); grizzly bears (the last known brown bear in California was shot in the 1920s. It is at the very least ironic to note that the brown or grizzly bear is the featured symbol on the state seal and flag); buffalo (there is a herd of about 200 animals on Catalina Island – they are bison-cattle hybrids; I am not sure about the genetics of the very small herd in Golden Gate Park in San Francisco; nationally, well down from the 60 million in the 19th century); bighorm sheep (maybe 600); and elk (4000 now if MAP does not wipe them out; were essentially extinct by 1870). Domesticated cattle are doing fine: almost 100 million in the US.