The following article is an overview of a talk given by Nick LaRocca, rosarian and past-president of the Jersey Shore Rose Society, at our October 23, 2010 society meeting.
The USDA Hardiness Zone that Nick refers to pertains to New Jersey.

Getting Roses Ready for Winter
by Nick LaRocca

1. How Cold Is It?
• If not properly prepared, modern roses (HT, FL, climbers) can be damaged by temperatures of < 10° F.
• Most shrubs and OGRs can tolerate much colder temperatures.
• USDA Hardiness Zone - Shore and south - Zone 7b   (see Hardiness Zone Map)
• Inland - Zone 7a
• North and West - Zone 6
2. What is Winter Damage?
• Rose cell walls contain water and it is the major component of plant tissue. When water freezes and expands at temperatures below 32 degrees, ice crystal formation develops in the living tissue and causes the cells to rupture. Damage occurs which can also result in death of the plant.
• As plants harden off, they develop a kind of anti-freeze to prevent this.
3. Hardening Off
• Plant cell walls thicken as they prepare for dormancy. This process is often called "hardening off" and occurs when the temperatures gradually decrease. The canes often give off a purple cast when allowed to properly harden. If there is not a gradual decline in freezing temperatures, the roses are more susceptible to damage when exposed to subfreezing levels.
4. Winter Rose Care begins in September - October
• Maintain your spray program. Use a fungicide to prevent black spot, mildew, etc. Add a contact fungicide if you haven't been already.
• Do not deadhead after mid-September in Zone 7b. Minimize cutting of blooms. Allow the roses to "go to seed" or "set hips". Pruning and dead-heading will cause sap to rise to form new tender growth, which will freeze when temperatures drop and cause damage to the plant. Allowing the roses to set hips will trigger their dormancy.
• Rid the bed of dead and fallen leaves as much as possible. Old leaves harbor spores of fungal diseases and the next generation of garden pests.
• Fertilizing: DO NOT FEED IN SEPTEMBER/OCTOBER.
5. Winter Rose Care Continues through November and beyond
• Feed Roses in November
• OGRs/Hardy Shrubs: regular feeding in early-to-mid November - about 1/4 cup of 10-10-10 per bush or about 1 pound per 100 sq. ft.
• Garden Roses: If you missed your August Feeding, you can do a "catch-up" feeding at this time.
• Check your soil pH (6.3-6.8) . Add lime during the winter to correct. Add at a rate of 1 cup to large bush (1/2 cup per mini) if pH much below 6.3. Scratch the lime into the soil taking care not to damage roots.
• After roses go completely dormant, spray them with a dormant/horticultural oil, or lime-sulfur spray to kill fungal spores and eggs from garden pests that could winter over. You can do this anytime the temperature is above freezing and as late as next March.
6. Winter Mulch
• A winter mulch - preferably organic - may be used to maintain a fairly constant soil temperature to help avoid the "freeze - thaw" seesaw.
• Applied over the soil - not over the plant
• Applied only after the plant has thoroughly hardened off and the soil is cold - think Mid-to-Late December
• Optional in Zone 7a
• May be needed in Zone 6