Thanks for the info. The landscaper said he used premium grass seed, though didn't see the bag. He's done a lot of work around here and I've never had an issue like this. He first laid down 30 yards of (what he said was) premium top soil, then used starter fertilizer, then seed and covered with straw. Is it possible that the straw was contaminated with these seeds? Is annual ryegrass the same as orchard grass? I'm concerned because he just scraped and seeded a 1/4 acre to expand my lawn which is now just germinating. I'm hoping I dont have this same stuff all over that new area too.

That's Marchantia polymorpha, perhaps the most common livewort worldwide. It is a bane to some commerical nursery growers when it get into their potted plants. I agree it is a cool looking plant. However if you are also trying to encourage the moss to grow as well then you will have to move the liverwort outa there as the liverwort will simply cover over the mosses in your picture. They are really neat to grow in a pot or any container with drainage. Just use a soil mix of half sand and half peat moss, get it wet, pull up some of the liverwort and press it into the soil and water with rain, distilled, or r/o water. I believe that they can handle some tap water better than can the mosses. Here is a link that might be useful: Google Marchantia images

you can avoid such.. if you sterilize your potting media.. prior to use ... see link ... you could gently scrape out an inch or so of media [i would just use a teaspoon] ... and replace it.. else.. there are probably a billion seeds in it ... such things.. usually need sunlight on the surface to sprout ... so by removing that inch or so .... you get rid of most.. and bury the rest ... it will have no immediate effect on your plant ... i suppose if you left it there for a decade.. and never fert'd.... it could use some nutrients .... there is a very active houseplant forum ... ken Here is a link that might be useful: link

The photo isn't entirely clear, but seems to be lichen growing on the woody stems. This is harmless to the azalea. It can be rubbed off, but you're more likely to a damage the plant by doing this than by just ignoring it.