Cassia tomentosa (aka:Senna multiglandulosa) - Wholly Senna

That gives a lovely effect

Yes, it really does...

I used to have a huge wholly senna when I lived in the San Francisco Bay Area. It was 20' (6 m) tall and spread 24' (7.4 m). It typically grows smaller.

The only problems with it, it has a lot of seeds pods in summer (the only season it doesn't flower) and seedlings pop up everywhere!

I prefer the size of this one in the picture.
Yes seeds every where would be troublesome for me.

Luckily, it can be trimmed to any size.

Great is it hardy?

It's tropical in origin. It's a pretty tough plant, though.

The tree I planted in the SF Bay Area survived the Dec. 1990 freeze (which lasted a week). It had a tremendous amount of freeze damage, though. It survived 22ºF or -5.5ºC on the coldest morning and came back strong during the summer. It doesn't like a whole lot of rain during winter, though.

It's biggest bloom-cycle is during winter.

I think our frost s would kill it being tropical Andy or our rain would kill it through winter

Most likely it wouldn't grow very well there. It does like a lot of heat and dry conditions to grow well.

Thank you Andy I shall look out for it here if not on the net.