The “Iceberg” floribunda rose (Rosa spp.), also known as Rosa “Korbin,” is the top-selling floribunda variety and one of the most popular of all roses. This shrub rose was first introduced in 1958 and has since garnered an Award of Garden Merit from the Royal Horticultural Society and a high 8.8 rating from the American Rose Society. Its white double flowers, each with 30 to 40 petals, bloom from June through October in U.S. Department of Agriculture plant hardiness zones 5 through 9. Fertilizing and Soil Maintenance For “Iceberg” roses to develop and remain healthy, well-maintained soil with appropriate fertilizer applications is essential. Problems with soil salinity and nutrient deficiencies make it difficult for “Iceberg” floribundas to thrive. High salt levels result in injury to foliage and plant dieback, and lack of nutrients like nitrogen and magnesium can cause yellow leaves, spindly growth and undersized blooms. To remedy these problems, ensure sufficient irrigation to keep salt below the root levels and adopt a regular fertilizer schedule. A slow-release fertilizer is recommended, with applications every six to nine weeks in February through June and again in September to mid-October. Adding a layer of mulch, about 4 inches thick, every year after pruning will also add organic matter to enhance soil structure. Irrigation Adequate water is also critical to keeping “Iceberg” roses properly hydrated, especially during the spring and summer months, when it is budding and producing blooms. Insufficient irrigation can lead to salt buildup in the soil, which has detrimental effects on the “Iceberg” rose's growth. Soil also should be well-drained. Precisely how much water to give can vary, depending on current weather and individual microclimates; however, a good rule of thumb is to water “Iceberg” roses two or three times a week during the spring, increasing to three or four times a week in summer. If you have planted an “Iceberg” rose in a container, more frequent watering may be required.