What will live under mature italian cypress ?

I've heard from an Italian friend that genestra(Spartium juncium) is an Italian wild flower that colonizes areas open to them...it is perhaps invasive and it would be a good thing to google it to find out if it is on a prohibited plant list in your state. It has small yellow fragrant flowers. worth a look perhaps?

Cerastium - Snow in Summer, Cerastotstigma -Plumbago -- sedums and gobs more. This is where I suggest, go back to the Nursery you bought them from and ask them. I am sure you will get some good suggestions. Then research them.

Some of these plants are useable, as they are so tough. They also can be weeds -- like the Spartium.

Rubus calciniodes might be another possiblility. A native plant nursery might be another thought. What survives under Redwoods would most likely survive. I am thinking of something but it does not come to mind, but it is a low growing groundcover in your neck of the woods.

My Spartium juncium is more like a shrub - its habit is to grow tall, but I prune it back to keep it under control. There's one in the village which hasn't been pruned and it is at least 12' tall and spread about 18' - it's like a wide tree and is very ugly as the lower part is bare. Certainly not a plant for underplanting, I wouldn't have thought, Lori! Are you sure that's the right name?? I thought the common name was something like 'Spanish Broom'.... I think.

I guess I was thinking about more about native partners...and less about ground cover...and yes it could be considered a weed...but it is beloved by some and seems to adjust well and quickly to any soil...it can be pruned low...as to Spanish Broom ...I just know it is native to the mediterranean. How about another mediterranean native like Rosemary? It is easily trimmed too, can even be formal if pruned and groomed.