The more sun you speak of is the key I believe! Just be sure to keep the roots cool. Despite the so called claims that they're bred to be heat tolerant, they will droop during the hottest parts of the day if their roots get warm. We've got two knock-outs and we've managed to keep them about 2-3 feet tall. very easy to prune back hard if they start getting too big for their spot- they don't seem to mind either way. im sure they could be much bigger if we let them go. also, you may try using alfalfa meal as a frequent fertilizer. work in two cups of it into the surrounding soil of the plant. try to work it in as deep ass possible without doing major damage to the roots. 2 cups may seem like a lot, but this stuff WORKS WONDERS when in comes to promoting blooms!! we use it on our tea roses as well. just continue to work it into the soil until the entire two cups is evenly incorporated. do it every six weeks and you'll darn near have continuous blooming all summer!
