I have three holly bushes in my yard (either American or English, not sure which). One is severely overgrown (at least 6 feet tall and about as wide) and the other two have some dead branches from snow damage a few winters ago. I would like to severely prune them all back to encourage new growth so I can get a better handle on maintaining them. Online sources say they will come back very well after being cut down almost to the ground, and that mid- to late-winter is the best time to trim. Is this info correct? Does anyone have any experience with taking hollies down to the ground? I'm in Rhode Island, Zone 6b. Thanks!