I see this type of Euphorbia during winter in the city of Vancouver. This one is located near the Victoria Inner Harbour in James Bay. I saw several other kinds this week. I talked to local gardeners removing stuff for winter or putting in winter plants. Two were from Ontario like myself. We find it amazing what little we knew as easterners about BC. I took geography in Ontario and Canadian flora was included. The course had obviously way too little content on BC. It was so generalized that it is actually sad to find how as easterners we were obsolutely ignorant about the BC coast and its potential. My gf is stunned seeing winter veggies. Some newbies are very surprised but are not complaining. Keep on gardening... Cheers Here is a link that might be useful: Winter Euphorbia

I agree w/ Biker that w/ so few leaves & no blooms it's tough to say. If as he suggests, it's a E. milii type, it should still be in leaf, all of mine still are & I'm in NYC (where it's been unusually warm, in the 40s & 50s in Dec.) Sorry, can't see the bloom in the pic at all. Does this thing bleed white when you cut/tear it? If so, pls. be cautioned about Euphorbia sap, if you know some succulents you may have heard Euphorbia sap can be a skin irritant (depending on the type of Euph), so pls. read up on that if you don't already know. I suspect it's rootbound & if it were mine, I'd turn it out to see what's going on down below. (My cynical side suspects someone dumped this on you as they didn't wish to bother w/ a repot of such a a large & spiny thing as this, you'll need gloves & lots of newspaper.)

I've just googled it and I think you are right. I didn't know that cacti could have white sap too!

I have seen info that says it is annual and different info saying it is hardy in z10 and up...I do not know for sure but suspect that it is tender perennial, not a true annual. Based on plant I have, later may be correct. I have the plant - was planted as ground cover with another tender plat, and it had survived 2nd winter now. It didn't look that great but I do not have GH. It eventually lost practically all the leaves and I was to pull the roots out but didn't bother - in spring, very few remaining 'sticks' (few tiny branches left and looking dead) started to sprout leaves. It is growing now again. I am sure that is not from seeds as I could see where the leaves are growing from. It may self-seed, but I don't see at new plants growing. Many Euphorbias self seed - I have this one that I leave to self seed thruout the garden (I pull any small plants I don't want): Euphorbia marginata - grows about 2' tall; looks like a small tree and bees love it :) What is your general location???