I agree, it's probably more of a windborne issue. I used miracle grow potting soil in all my containers and I have no weeds. I'm on an 8 story balcony, so while I am definitely pulling fluffy white weed spores out of the pots I'm probably not getting the same kind of weed seeds I'd have if I were near the ground. Try mulching your containers to keep the weeds down.

1st and maybe 2nd is better in pots but subsequent years is better in ground regardless of the size of pot I've tried. 10 year old P. suffruticosa at 4' tall, 5' wide. hint....use html image tags (put a before and after to make it work) img src="web location including http part" alt="photo caption" width="640" height="480" /

Mushrooms are just the visible signs of the fungi that live in any sort of soil, typically feeding off the decaying organic matter. Very common and completely harmless to the plant. They are not necessarily related to humidity. In fact, I'd go so far to say that your tree looks to be suffering from a lack of humidity/soil moisture :-)) What kind of potting soil are you using? Looks pretty finely textured and depleted and the tree would likely benefit from being repotted with fresh media and a good, thorough watering.

@HighColdDesert: I find that everything I grow, always grows better in the ground than in a container (when cultural conditions are appropriate). I just dont have a sunny area where I might be able to plant oregano in the ground so I am starting it in a pot. But, if it is as easy to grow as people are telling me, I might it try it in the ground somewhere next season...I would really like that. There really is no comparison, at least in my hands, between growing in a pot vs growing in the ground. Folks who do grow oregano: is there an improvement in flavor when grown in a hot dry area vs a more shaded and moist area?