I have a mature wisteria that blossoms every year. It has several limbs coming off it. I have grown it primarily over a pergola (where the old wood is) but have recently encouraged it in another direction which is doing very well. Question: How to discourage growth over pergola and encourage in the other direction without harming it? The limbs in the other direction are established and blossom but a quarter the thickness of the main limb. Any advice would be greatly appreciated.