More than likely what comes off that tree is Lichens and not moss, although both are first stage plants Ma Nature grows to add organic matter to soil so higher order plants can grow in that soil. Lichens grow on trees where dust from the air accumulates in the bark and traps just enough moisture for those plants to grow. What is knocked off by the birds can be left where it falls, mixed into the soil, or picked up and composted.

Thanks!.I'm over here in the eastbay,Hayward. I think the Hercules flowers are the only pics on the net.No matter how much i looked,didnt find any.So,even i was wondering what they were going to be like! My advice to anybody is if you want a branching tree Aloe-Hercules might be the hardiest.If you want a tree Euphorbia cactid,E abysinnica might be the hardiest of those and E.ammak the fastest growing(haven't tried E.ingens)and almost the same in cold hardyness.E.ingens could be best of all.A neighbor planted a 6" dish garden plant 5 or 6 years ago and its a very bushy 6' now. I didnt see a bit of damage from the freeze on it..and they have it in the middle of the front yard-no cover whatsoever. Global or urban or both warming has really added to the menu of tropicalia to be grown in the bay area. If it keeps us above 32..the sky's the limit..

I would like to tell you the answer but mine start producing seed so fast I have never seen a flower. They take a while to mature but are easy to germinate in a baggy.

Yellow/green plants sounds like something variegated. If so, too many possibilities to know which you've seen. Wax Begonias can take being out in the sun, but all day in Atlanta might be a bit much. IME with putting them in tons of sun, they will stay alive and bloom, and definitely develop a deep red color, but don't grow as quickly at all, not by a long shot. I'd recommend trying to find already-nice-size plants if you try this. Dragon wing would be another to consider. The leaves are green, but it makes a good amount of reddish (possibly more pink in some light) blooms. That kind would be a bit taller. Other red plants that might be enjoyable, small enough to go at the base of a mailbox... Alternanthera dentata, Swiss chard (green leaves with red stems & veins,) Coleus cultivars for sun. Dragons' blood Sedum might be a nice ground cover under the taller things, but would creep into grass without a border/barrier.