Saturday, December 1, 2012

OVERWINTERING ROSEMARY (Rosmarinus officinalis)

Rosemary plant
Perennial - evergreen
Height: 2-4 ft.
Culture: Sun; good drainage
Flowers: Pale lavendar in summer
Leaves: Herbal uses such as seasonings
Fruits: None
Hardy: Zones 6-11 (Franklin County is Zone 6)
Needs winter protection
This time of year a question often comes up: "Can I leave my rosemary plant outside during the winter?"

It depends on the plant variety, health of the plant, where it is located in your landscape, soil conditions and the severity of the cold.

Currently there are five rosemary varieties that are likely to survive our most severe winters: 'Arp,' ' Hill Hardy,' 'Salem,' 'Nancy Howard,' and 'Dutch Mill.'  Not all plants listed as hardy will be so for every gardener in the same area. While the rosemary variety 'Miss Jessopp's Upright' has been sold as winter hardy up into south central Pennsylvania, it is inconsistent in its hardiness, dying off in areas as far south as Virginia and yet overwintering in some lower Pennsylvania counties.

'Arp' Rosemary - winter 

Rosemary should be planted before June 1 to allow it to get well established and regular care will result in a healthy plant. Plants sited in sheltered areas, such as near a wall or fence, will get some protection from wind damage and dehydration. Rosemary needs good soil drainage and benefits from southern exposure for the most winter sunlight.

Some Winterizing Tips

Even for winter hardy plants, gardeners can protect against the cold.

In addition to cutting weak, dead and damaged branches, trim any branches that are too low. Fall is not the time to do pruning on rosemary as it will promote new growth that is highly susceptible to frost. Give the plant a deep watering and mulch around the bottom of the plant.

Sheltering windbreak for overwintering evergreens

Depending on your site, a small wind break made with tomato stakes and cloth or burlap stapled to them can help.

In our area, rosemary plants need protection from frost, snow and ice as well as wind during the winter. A good way to provide this is to cover or wrap the plants. To provide plant and branch support from heavy snow and ice, wrap the plant with burlap.

Start at the bottom and gently pull the branches loosely together. Overlap the burlap as you wrap to the top, leaving enough burlap to fold over and clip. This will give keep the branches from extending out and collecting the weight of snow and ice on them. Wrap twine loosely around the burlap to secure it.

Wrap rosemary plants with burlap and twine

Alternately, put a tomato cage around a plant, or stakes, and wrap them with burlap, leaving extra at the top. The cage or stakes need to be in place before a hard freeze. Fill the inside space loosely with leaves and clip the burlap closed at the top. The leaves help insulate a plant.

Fill with leaves to help insulate the plant

Check back later for tips on overwintering herbs indoors.

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