How about a Nannyberry (Viburnum lentago) or Wayfaring tree (Viburnum lantana). They are hardy in your zone and can be shaped into nice small trees. You can see my Wayfaring tree in front of the big old cedar in this picture from late May:

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That is pretty...I really like the nannyberry too. Gives me a little food for thought! Thank you!

Kristy

I am not familiar with the sumac you refer to so I'm not sure what look you are going for. But Ninebark 'Diablo' gets quite large and has arching branches. The dark foliage adds a lot of interest. Also Amelanchier (serviceberry)can be grown as a tree or shrub or somewhere in between depending on pruning out trunks at the base. If you want to attract birds, it is great for that. They love the berries.

I really do appreciate the input!

We were sitting out on the front porch last night - the sun was hot and trying to stream down on us...and that mountain ash is still there doing a wonderful job of providing lovely dappled shade. I just don't know what we're going to do! The tree is about 8+ years old and maybe about 20 feet tall. It's perfect!! Except for the fact that its roots refuse to remain stable. But I'm now thinking that another tree is the route we'll have to go.

Thanks again!!
Kristy :)

If you're in full sun you need a plant that likes that, so my thoughts - elderberry, heptacodium - might not be ideal, but would also work. But there are many smaller, understory trees that max out at about the height you have in mind.

Fall is a better time to plant than mid-summer, so can you keep the ash for the summer?

KarinL

I would second a heptacodium - I love that tree! - except I checked and it's only listed as hard to zone 5 so would be risky for you.

Heptacodium is hardier than usually stated. It will do fine in the Twin Cities area. It is a nice tree/shrub. Mine is about 15 feet after 6 years from a #1 pot. Flower buds starting to poke out.

I have found the Magnolias Elizabeth and Butterflies to be quite fast growing as well and hardy. Wonderful, fragrant yellowish flowers in the spring.

I've never heard of a heptacodium. I'm looking for small trees or tree-form shrubs for our "hellstrips" which are between 5-6' wide. Is this something that would thrive in my zone? I'm in Monterey County,Central CA. Any other suggestions?