Agree with Floral_uk, it looks like one of the black nightshades, probably S. douglasii given your location. There are several very similar species, and they grow wild pretty much everywhere. I take great pains to ensure that they never go to seed in my gardens, and they still crop up from dormant seed or from bird droppings. When I lived in San Diego, the local Hmong community cultivated one of the black nightshades extensively. There is a pretty god write up of the various species & their properties in the link below. Personally, I would just treat it like the weed that it is & dispose of it. Really nice jade plant bush behind it, by the way. Here is a link that might be useful: Black nightshade

I would love to grow that Maple but alas, no room. :o( The ground cover amongst your Violets is Wandering Jew...a weed. Can cause skin allergies on dogs. It is hard to get rid of because anything left will grow back. Vigilance is needed. The garage wall has Ficus pumila, creeping fig. It is pretty and useful but if not kept under strict control, can turn into a monster....you might want to Google information about it before the trouble begins. The small plant with the shiny leaves is Coprosma. Considered a weed in Melbourne. An untidy bush that is hard to keep to a decent shape and reseeds everywhere. I would pull it out now while it's small. Sorry to be so negative, just being honest. Dee.

Oh, that explains it! I was searching in the wrong genus! Thanks for your help!

This species self seeds all over my allotment. You don't harvest it leaf by leaf. Just cut off a whole plant. It needs thorough rinsing because being a winter salad it gets a lot of mud splash and can be gritty if not carefully cleaned. The leaves are larger on the basal rosettes. Once they start to flower the leaves get smaller. But they're perfectly edible at any stage, including the flowers. And superior to lots of other wild greens imo. There are commercially available cultivars with larger leaves.