How far apart should climbing hydrangea vines be planted?
The plants you are starting with (4″ pot) are pretty tiny! Usually the first year deals with root development , the second year they start to put on some real growth and usually by the fourth year you will get a decent show. They are a little slow to get going but once they do they do get enormous! The ones you have being so small I would add an extra seasons growth to that. As for distance apart it depends what you are aiming for. Each plant has approx 40ft height and about 20ft spread! http://www.monkswaygarden.co.
