By Andyandchris
United Kingdom 
We have a mature white wisteria in our garden that has suddenly started to produce some blue flowers amongst the usual white.
Is this unusual and what would cause it to happen as it's never happened before.
20 May, 2013
If the blue flowers are all on one or two stems/branches, its most likely reversion - the natural colour of these plants is lilac blue, and the white version is a cultivar, so parts of the plant may have reverted to the original genetic programming. If they are all on one or two stems, with no white flowers on the same branches, then you can remove those branches right back to the main stem if you wish to do so.
20 May, 2013