Ask the Master Gardeners
Q: For years I have been growing rosemary in pots. Recently I heard that hardy varieties are now on the market. Is there a variety of rosemary hardy to our area?
A: While temperature plays a major role in winter survival of rosemary (Rosmarinus officinalis), the quality of the soil and the planting location are important factors, too. Rosemary is an evergreen shrub native to the rocky hillsides of the Mediterranean region and Portugal.
It was introduced to the United States by the first colonists; in the North, they grew it in pots to withstand the harsh New England winters.
Today, more than 50 cultivars of the two forms of rosemary, upright and prostrate (R. officinalis prostratus), are grown in the U.S., but only a few are considered hardy to USDA Zone 8.
Among them are â€œArpâ€ (named after the Texas town where herbalist M. Hill discovered it on a snowy winter day) and â€œHill Hardy.â€ Both have been grown successfully at the U.S. National Arboretum, where they have survived several winters at very low temperatures, with little or no dieback.
As a result, these cultivars have been given a temperature rating of -5 degrees, giving hope that rosemary may also survive winter in colder USDA zones.
Rosemary thrives in light and well-drained soil, with full sun exposure and good air circulation. Its chances of winter survival are improved by planting it in a protected location, near a fence or wall, and by using a cover or a blanket of leaves.
Experimenting until one finds the appropriate â€œmicroclimateâ€ is the practice that has allowed some gardeners to overwinter rosemary outside in colder climates.
In our area, potted rosemary still remains our best choice to enjoy this fragrant herb year round.
â€” Cristina Malinverno, Blauvelt, master gardener, Cornell Cooperative Extension, Rockland