Better to repot into the next size pot and so on up in size. Plants and shrubs doing like to be in over large pots. Of course if your shrub is huge that is a different matter.

I usually go up a size at a time but you can put in a bigger pot if you prefer, I have done so before with no problems. Everyone always has their own way of doing things. I have lots of large pots and a few massive ones all with shrubs and trees in.

My preference is to fill the bottom of the pot with about 2 inchs of stones and a thick layer of sharp sand which I mix into the stones a little, I then put on a thick layer of good compost (I use miracle grow) up to half way past the roots I then use top soil to fill up the pot. If I intend to keep the shrub/tree there I finish of with a layer of white stones which looks nice. But I add a thin layer of sharp sand first before I put the decorative stones on. I have done it this way for years and my shrubs and trees are all doing great. But as I said this is my way others may suggest other options. :)

Thank you for your views.....I do find Sharni07's recipe quite interesting. I usually just use stones at the bottom followed by compost (sometimes Miraclegrow) -no sand & no topsoil. Perhaps that would explain why some plants don't do so well..... I had been thinking of returning to a top dressing of stones -just to deter the squirrels. In the past I tried that with some success. This season has been a nightmare with these pests- especially since I'm using bark to top-dress.

The sand aids drainage from the roots but holds on to water and nutrients that would otherwise be lost. I find if I just use compost alone I have to constantly replace the top layer and my plants have not been so happy or grown much, the roots just don't like it especially so with shrubs and tree's which became evident when I had to replant them. I use large pots so find adding about a third of top soil a third sand and a third compost helps my shrubs/tress establish good roots and keeps them happy in their pots. The stones.. I just like them. :)
As I said before everyone is different but I have tried many other ways before I settled on this one, I started out my gardening 8yrs ago with only large pots to use and no garden so it was all trial and error really. :)