Growing rosemary successfully outdoors on the edge of zone 5
posted by on 05/13/08
Rosemary is a delightful herb best suited to warm dry climates and sandy soil. Our family has been impressed with the world of difference a little rosemary makes in our stew recipe. I know that there are many people who would like to grow rosemary but their climate is not favorable. Being on the edge of zones 5 and 6 in the mountains of West Virginia, our climate is the opposite: cold and damp with clay soil. Each winter the temperature drops below zero F once or twice. If I had known about others’ failures in attempting to grow rosemary in my kind of environment, I might not have attempted it. But since the family enjoys using rosemary so much, when I heard about a variety that was “hardy to zone 5” named ‘Madeline Hill’ I decided to give it a shot. It is important when trying something new to keep detailed records. Only then can all the factors be considered for helpful conclusions. I hope the details here will be helpful to someone.
I planted it in April ’06 in front of a small south-facing brick wall but the soil was heavy clay that had been amended with peat moss and gypsum. Because neither clay nor peat moss is recommended for Rosemary, I amended it further with sand. The wall is 7 feet from the outside wall of the house so I do not believe it receives any warmth from that source in the coldest days of winter. However, the eave of a porch roof helps keep the soil somewhat dry and that is a good thing for Rosemary.
It seemed to grow happily the first summer. The following winter I insulated the plant if the temperature threatened to go below 15 degrees. I did this by turning a crate over the plant and wrapping it thickly with burlap bags. “Thickly” means about 15 layers. Since a bag is two layers, that means a 7- or 8-bag thickness all the way around. In a 12-day period in February 2007 the temperature fell to single digits seven times, the coldest temperature being -2 degrees F. The temperature rose