What kind of weed is this, is it harmful to leave it alone?
 

Or should I remove it? I was thinking, maybe wrongly, that since it's not very deep rooted and doesn't compete much for nutrients and water for my other plants, maybe I can leave it alone as a "ground cover".

Thanks,

Re: What kind of weed is this, is it harmful to leave it alone?
 

It looks like either spurge or prostrate knotweed. Both are prolific seeders and you'll be sorry if you let them go to seed.

Re: What kind of weed is this, is it harmful to leave it alone?
 

Get rid of it. I pull and then use roundup on the remainder.

Re: What kind of weed is this, is it harmful to leave it alone?
 

It is spurge. Every leaf you see has already deposited at least one seed.

Re: What kind of weed is this, is it harmful to leave it alone?
 

Ok I'll remove them asap, they can be pulled up en masse pretty easily.

Re: What kind of weed is this, is it harmful to leave it alone?
 

I would have wondered whether to remove it or not also as I'm always on the look out for pretty landscaping plants that come up wild and survive on the area's rainfall alone. Unfortunately I've found that the hardiest wild plants are the most invasive!

Re: What kind of weed is this, is it harmful to leave it alone?
 

Definitely get rid of it before it causes you problems. It's just a matter of time!