In the small bit of front garden I currently have one hydrangea and an sortment of other plants that don't grow well. All the plants came with the house. Can I pull out all the other plants and put in more hydrangea and then put pebbles around them?
Due to the trees and the state of the neigbours' garden I get lots of weeds and sapling growing in the front which take lots of maintance but I am worried that the pebbles will stop the plants from growing.
Pebbles won't stop hydrangeas growing. They'll act as a mulch and help keep the soil moist.
What you will find, though, is that lots of weeds love growing in them; the smaller the pebbles the worse this will be. You'd be better off mulching with a thick (six inches minimum depth) of bark chips or Strulch.