Is there a ground cover plant that is tree friendly and weed "unfriendly?"?

Vinca Minor

Any kind of heavy grass that thrives in partial sunlight. Sodding the area might give the grass a “head start”. Close around the house, we use tight-mesh cloth covered by crushed stone, we then place potted plants on top of this; looks very orderly.

I love Irish Moss!

It does well in part shade and is so cool, fist size mounds of dense bright green mossy balls that grow together to form a walkable, lumoy carpet like 100’s of little islands. NO weeds can grow in it’s density, and it looks really neat. great for hillsides too!

I second Marine life with Vinca.

Just don’t use English ivy – it will smother the cypress.

Vinca is a good choice, or pachysandra (Japanese spurge). Just be aware that you’ll need to control them somewhat, they’re both invasive and will spread.

This site has a nicely comprehensive list, including quite a few plants that I’m not familiar with.

My mom grew something she called ‘snow on the mountain’. I don’t think anything would kill it. I know she never watered it.