I have caragana and cotniaster bushes all over the area here and am thinking of transplanting some to make a hedge ,I'm wondwering which is the fastest growing and what to do to make them grow faster .
Lois Hole's book "Favorite Trees & Shrubs" says that Caragana grows faster than Cotoneaster ... Caragana 2+ ft. per year, vs. Cotoneaster's 1-2 ft. per year.
As to how to get them to grow faster, I have no advice beyond what any gardening book will tell you (soil prep, right plant for that site, tending them)). Personally, for faster growth, I subscribe to the "Cross Your Fingers" school!
Go to: fast growing trees.com
I have carraghanas here. I give mine liquid fertilizer. And water them every week and they will grow quickly. Also give them a light pruning every couple of weeks to get them to grow bushy. I grew mine from seeds. You have to put the seeds in the freezer for a few weeks to break the dormancy on them though before u plant them.