It is usually grown as a large shrub, 10 feet high by up to 15 feet across with foliage to the ground. It was a chance seedling in 1964 at Santa Ana Botanic Garden. It makes an excellent background plant, fast growing and tolerant of normal garden watering, but not requiring it, in most areas. I would want to see a specimen grown as a tree before deciding I wanted to prune to that shape. A good choice. Al

Interesting - the local nursery was just recommending the same to me, she also said it can be shaped into a tree form. She showed me a picture in her catalog of a tree form. I found this picture online but it's not "frosty blue".

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and here is a UK nursery selling Ceanothus as a patio tree

Wow -- gorgeous!

I've decided to abandon this idea because the size would completely engulf the area where I was planning to put it, and shade a nearby rose.

I have seen ceanothus 'Ray Hartman' grown as a small tree. Ray has beautiful large (for a ceanothus) glossy green leaves. .. So if you wanted a small purple-blue tree, a non-native blue is the new, charming, bonsai blue jacquaranda which can get 10-12'H and 6-8' wide. I know this answer is well after the question; just putting it here for posterity.

I killed three Ray Hartmans in a row. I planted a tree form South Coast Blue in the same spot and it's been growing rapidly. It's got big flower scapes (I think that's the wrong botanic term) of medium blue flowers.

I love it,have no space for it though.I love blues and purples in the landscape.

Thanks for writing about that Jacaranda - I have the perfect spot for that (if my strawberry treelet dies, which it looks like it might).

I also have a Ray Hartman (6 months old) that I'm growing as a tree. Going well so far.

Btw local people around my area (west side LA) are saying that ceanothus don't really do well in full FULL sun. They are having better luck with a little shade. Cannot vouch either way for that though.