It may be skunk cabbage. Here is a link that might be useful: Symplocarpus foetidus

Hi there tedhort, Excellent! I googled for the name you gave, and yes - that's the one :) Thank you so much for your help! Now I know how NOT to kill it lol :D Shanook.

more info: the vine was first noticed 10 years ago, 5 years after purchasing the house. it does not come up every year. it's had little to no care. last fall the city hacked everything back after a summer of neglect. all clippings were tossed into the cypress (mulch & frost protection maybe). the soil pictured above is what it's been growing in. it has shade at the bottom and climbs to the sun. it is sheltered from direct sun & wind. i believe it is on the south side of the house. all around the base of the cypress, flat shoots pop up where sun barely dapples through. maybe they send roots back into the soil as they grow along the ground, until they reach the edge of the cypress, then go up to the sun. i exaggerated in saying it's climbed 40', as i was having a double rainbow moment. but it's definitely about 20'. :D thanks so much for the help. ~spazplant

Thanks for the pointer. It is indeed an exact match for Solanum americanum, a.k.a. American black nightshade, Small flowered Nightshade, common nightshade, white nightshade. And as Ken points out, CalFlora lists its toxicity as MAJOR. Cheers for the ID. Out it comes!