Answer: I'm not convinced that pulling the stick out of the tangle of stems was the best suggestion. Especially if the vines were tied every few inches. I probably would have done what you did - try to untangle everything and then plant the ivy. The vines will need some support until they are able to find a way to attach themselves to your rock wall. They will eventually, and once a stem attaches itself, other vines will follow and entangle themselves in the pioneer. I think you'll find that as the plant matures the stems will be much thicker and sturdier and will begin growing upright before they even attach themselves to the wall. The stems that you're supporting with string will produce lateral vines, which will find little cracks and crevices to hold on to.
Since you have 200' of wall, you might want to purchase flats of plants rather than individual pots. Flats can be divided into 3-4 dozen rooted plants. Ivy grows quickly but you can space them 6-12" apart (depending upon whether you're using divisions from a flat or 4" individual pots) for fast coverage. The plants will first spread along the ground but then the vines will climb over one another and begin to grow upward, supporting one another as they grow.
Best wishes with your new ivy!
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