We have just come back from a holiday in the north of Spain, Midi-Pyrenees and the Dordogne.

We noticed large numbers of a large very pretty tree which had long hanging branches of white flowers (looked like laburnum flowers but white not yellow). The leaves were divided up into smaller leaflets, just like Ash.

In places there were so many of the trees that the hillsides looked white.

I've not been able to identify this tree. Can anyone help out. It must be a native as it there was so much of it everywhere.

Could it be a European Olive tree? They grow in that area and have white flowers in the spring.

here are photos of the Spanish olive tree.
https://www.google.com/search?q=span...w=1366&bih=589

Robinia?
http://en.wikipedia.org/wiki/Robinia_pseudoacacia

Pine/Fir and French oak are the dominate trees species in the Midi-Pyrenees. There are also maple, chestnut, walnut and linden trees. What you saw was probably a flowering chestnut (white flowers).

Olive trees, Spanish or French, do not grow in the midi-Pyrenees.

"Olive trees, Spanish or French, do not grow in the midi-Pyrenees."

They do. There is even a thriving olive mill in Cordes-sur Ciel

How big are the trunks of the trees, or are they actually bushes? It could be any number of things.

Did they have a strong, perfume-like smell?
The comparison to laburnum makes me indeed suspect robinias. They bloom later than most other trees, i.e. in late May and early June = now.

Chestnut trees have "candle" flowers that are standing upright, not hanging.

Looking at the possiblities suggested, Robinia fits the bill. I'd originally discounted it as I thought it was a North American tree. However doing a bit more reading around the web it does seem to have been introduced into France and presumably has spread and spread?

We saw plenty of oak, maple, walnut, sweet chestnut as well as lime. It wasn't olive or horse chestnut which I am familiar with and can recognise. It was also a pea family flower like the laburnum.

There must be implications for the native woodland as in places it was the dominant tree.

Even in the Southwest of Germany we have areas where robinia trees dominate forests, around Saarbrücken for example where entire hill slopes are covered in them. This species has happily settled in Europe.