Ruthless advice on planting needed
Left border is north facing. You can see a mature hawthorn on the E border and a prunus on the N.
There will be ferns, solomons seal, climbing hydrangea etc to cover the walls ASAP.
However, I think I may already have gone wrong.
I've stuck a couple of snow queen himalayan birch trees in between the more mature ones which you can see in the pic circled red.
We also have a mahonia charity on the way which I think should take up the top left corner space, but would get in the way of the birch. By all accounts it will get quite big.
Have I made a massive mistake? Should I take those birches back out and leave the three more mature trees as they are, and stick to smaller plants in between? If not, where will the mahonia shrub go?
I'm also not sure I can bear waiting 5 years for any sort of impact from the birches. They cost a good £75 each and the mahonia wasn't cheap either, so I'd like to make all three work if I can!
Any guidance appreciated. I cannot make my mind up at all and need someone to tell me exactly what to do, as I'm going round in circles :-)