Plant@Net has come up with Artemisia verlotiorum, Chinese mugwort, with 54.89% likelihood, Artemisia vulgaris, Mugwort or common wormwood, at 33.45%, and Artemisia princeps, Japanese mugwort, at 10.94%. They have some other Artemisia suggestions at very low likelihood, and no non-Artemesia suggestions. I would think Artemisia vulgaris, but the habit of the one in the UBCBG Physic Garden is so different (upright stems about my height), at least when I photographed it six years ago, and the flower heads here seem to be a different shape. The Artemisia verlotiorum photos I see don't look very convincing. This is in a landscaped area next to an apartment building in my neighbourhood. I had thought the leaves were 3-4cm long and thin, but I see that's only around the flowers. Those leaves are white on the undersides. Lower down on the stems, they are very deeply lobed, three or five lobes, and I didn't notice the undersides. Leaf margins are entire. All the leaves are soft. Stems are reddish-purple, and seemed square with white edges. The leaves had no scent, but I did notice a faint wormwood scent from stroking the flowers.
If it was here, I'd say Mugwort (an abundant native species here). In Vancouver, sorry, wouldn't like to say if other similar exotic species are commoner or not.
