[willowman]

We have a beautiful old wisteria growing over a pergola; it is always admired because it is white and there don't seem to be many white ones around.

However this year I noticed one of the branches is producing blue flowers.

How is this happening? Is it reverting to its original colour and is this likely to spread?

[Spana]

I think the best wisteria's are grafted  as opposed to seedlings. So perhaps you have a shoot coming up from below the graft,  your root stock being blue with the white grafted on to it, but someone will know for sure
I've had Dalia's and oriental poppies change colour which is even more weird  :blink:

[Flowerpower136]

Agree with Spana, sounds like a shoot from the orignal rootstock.  If you trace the branch back, you can check if this is right or not.

If you want to keep the whole thing white, you need to take the blue shoot off at the base as it's likely that the blue rootstock will be stronger than the grafted white one, so could eventually outgrow the more delicate white variety.

[willowman]

Thanks for the advice.
I have followed the branch back and cut it off, so we'll see what happens next year.
It gives such a wonderful display of white flowers and the scent, especially in the evenings, is astonishing.