There are a number of decisions the home gardener makes that directly affect the appearance of the roses in the garden. These decisions include choosing the type of roses to plant, choosing the location, digging the hole, deadheading, pruning, mulching, fertilizing, and watering. Many of these decisions are related to climate, and the effect produced by each on the roses.
The climate in each of the rose zones has a favorable or unfavorable effect on the rose. Zone 1, or the uppermost zone in the USDA map system, has a temperature of 28 to 30 degrees F. Zone 2 is hotter, with temperatures of about 35 degrees F. in the southern latitudes and much cooler north latitude. The temperature fall in Zone 2 is about 10 degrees F cooler than in the comparable region, Zone 1. When roses are planted in Zone 2 they often do very well, especially when planted in rich moist soil with plenty of organic matter. Those roses that are developed to Zone 2 standards actually have been bred for this very purpose. They were bred to survive the harsher winters in Zone 1. While many roses, especially climbers can survive in Zone 2, it is not recommend that Zone 2 roses be planted here.
Zone 3 is the coldest climate in the USDA map system. The winter temperature is about 5 degrees F. in the southern latitudes and about 18 degrees F. in the northern latitudes. Zone 3 has a number of cold air rivers that originate from differences in elevation.Combined with the fact that the winters are much colder, makes it discourage to plant roses here. When roses are planted in Zone 3 they often do very well. It has low winter temperatures, with a growing season of 85.4 weeks. The growing season in Zone 3 is slightly shorter than in Zone 2, 14.8 weeks. When roses are planted in Zone 3 they often do very well. It has low winter temperatures, with a maximum winter of minus 34 degrees F. in the southern latitudes. The growing season in Zone 3 is slightly higher than in Zone 2, 19.8 weeks.
Zone 4 is the warmest climate in the USDA map system. The maximum winter temperature in the southern latitudes is 38 degrees F. and the minimum winter temperature is 20 degrees F. in the northern latitudes. Growing roses in Zone 4 has a maximum winter temperature of 50 degrees F. and a minimum winter of 34 degrees F. In Zone 4 there is a slightly higher minimum winter of 36 degrees F.
Zone 5 is the coldest climate in the USDA system. The maximum winter temperature is 42 degrees F. and the minimum winter temperature is 24 degrees F. in the southern latitudes. Zone 5 has a slightly higher minimum winter of 38 degrees F. and a higher maximum winter of 50 degrees F. In Zone 5 there is a slightly higher minimum winter of 40 degrees F.
Zone 6 is the intermediate climate. The growing season is between 55 and 65. The minimum winter temperature is significantly higher in Zone 6 at 60 degrees F. and the maximum winter temperature is significantly lower in Zone 6 at predictably 36 degrees F. This zone is split between zones 5 and 8. There is a third zone that is an area of continuous cold winter with a 5 to 35 year period of relatively cold weather, in the far north. This zone can be reached by planting roses that are designed for this climate which are properly pruned, trained and maintained.
Zone 7 contains the two coldest climates in the USDA map system. The winter minimum temperature in Zone 7 is 34 degrees F. and the maximum winter temperature is 41 degrees F. This zone can be reached by planting climbers prepared for cold winter weather and by selecting roses that have a hardiness zone rating of not more than 7. The important factor in determining the type of climbing rose that will perform in this climate is the length of the growing season. Climbing roses that are properly cared for to the USDA system’s recommendation of not more than 7 years, can be planted almost anywhere.
Zone 8 is the warmest climate in the USDA map system. The winter minimum temperature in Zone 8 is 45 degrees F. and the maximum winter temperature is 50 degrees F. This zone can be reached by planting hardy and heat-resistant roses that have a reputation of thriving in very cold climates and should be placed in commercial modular buildings. The key to the high winter hardiness of the climbing roses that one requires here is the same as with Zone 7, namely, that the climbing roses are hardy and heat-resistant.
Zone 9 is the second warmest climate in the USDA map system. It is only surpassed in this climate by the warmest climate,Zone 8. Here again, it is important to select the appropriate type of climbing roses for the cold winter months. Again, the climbing roses should have a hardiness zone rating of not more than 7.