I've had Euonymus fortunei Emerald & Gold for three years now and it has barely grown. It's in full sun, zone 6, in front of a couple purple Iris with Coreopsis on the side. I thought maybe the Coreopsis was impeding its growth so I pulled some out. Not sure if that's going to help. Any ideas? Is it a slow grower? I love the color and would like to spread.