Are you forcing/training it to go in the desired direction somehow? Some people attach the trunks with small wires or nylon stockings so they go where you want and not where they tend to go towards. Maybe sunlight is attracting them and they go sideways to reach it? Is the general area where it starts to turn sideways in the trellis somehow hot? I know that may sound like a strange question for the trellis but vines resist attaching to a hot area in walls and I was wondering if there was something NEAR the trellis area where it begins to grow sideways. A hot air exhaust or window or something that could explain the behaviour. But bottom line, you need to correct this tendency by forcing it to go where you want.

Thank you so much for your reply! I'd thought I'd read in Dirr's excellent volume on Trees/Vines, etc that Climbing Hydrangeas start slowly, but that once the root system becomes established, they grow more rapidly. Thank you so much for your encouragement! Dirr also refers to the Climbing Hydrangea as "the best vine." I am more partial, actually, to wisterias, but they get so rampant, and put out so many runners that they can be troublesome. I planted several at the bases of some large Maple trees on the property, as I figure they can go as wild as they want on the trees. But a wisteria against the house? No thank you. Thanks again!

I am not experienced with growing hydrangeas. I was gifted a climbing hydrangea and my preferred place to plant it is on a mulched slope, where it can grow up a large deciduous tree. The tree gets full sun, but of course the hydrangea would get partial shade beneath it - the leaves are already in now. The slope faces southeast and the soil is not good - full of rocks and cobbles and low in organic material. I live an a hill and my soil is the same everywhere - needless to say I always have fun trying to plant. However, I can dig a large hole and amend the soil as needed. I read somewhere plant on the north side of the tree, which would work well logistically. Any tips for success would be greatly appreciated. I am not even sure if climbing hydrangease enjoy the same conditions as "regular hydrangeas". I am assuming I will need to provide water, since the tree canopy is pretty thick. TIA, Pete

Color is going to be difficult in a climbing hydrangea - your choices are limited to white, white or white :-) There is a hydrangea relative, Schizophragma hydrangeiodes, (aka Japanese climbing hydrangea) that comes in a pale pink coloration ('Roseum'), but that's the extent of color choices in a climbing hydrangea. Not many climbers will attach to brick or other masonry - you need ones that attach with holdfasts or rootlets that develop along the stems rather than twining or vining climbers. That limits you to vines like the hydrangeas, Virginia creeper/Boston ivy or English ivy and none of these produce brightly colored flowers (or even very showy flowers). Where are you located and what is the aspect of this wall (north, south, etc.)? If you can provide some sort of support system, it is possible you could grow a climbing rose or wisteria against this wall.