Iceberg roses are one of the oldest and most beautiful of the climbing roses. The blooms are so white, they are almost blinding. However, they do not make good cut flowers for two reasons. Their stems are very thin, and they do not stand up well in a vase, and the blooms grow in clusters, so it is hard to cut without cutting off the new buds as well. But they make a spectacular display along a fence, on a trellis or over an arbor. These steps will help you with the pruning process.
Understand that iceberg roses should be pruned in the spring, when there is no danger of frost. Iceberg roses are hardy in zones 4A to 9A, so the exact time will differ depending on where you live. Roses are resilient, but if frost gets into a new cut, the stem will die. In the worse cases, you could lose the whole plant. Iceberg roses then need to be pruned during the growing season, and once again in the fall when they are prepared for the winter.
Keep in mind that spring pruning for iceberg roses is done in two different ways, depending on whether you want the roses to grow as shrubs about 3 to 4 feet tall, or grow taller as bushes. In order to make them grow as shrubs, you need to do hard pruning. This means cutting back the heavy wood more severely. But, this will keep the amount of flowers low.
Know that if you use the one-third method, you will encourage the roses to grow taller. Remove just a third of the oldest growth. This will leave you enough woody growth for new shoots to sprout from. Now choose a third of the best from last year's growth to replace the old ones that you cut away and remove the rest.
Remember that summer is the time to prune and shape the plant. Remove about a third of the flowering canes. Trim them short, to right above the five leaf section. There are two types of leaves on a rose plant. Some have three to a stem. Some have five. Look for the five. Also, remove the dead flowers, being careful not to cut off the close buds. Since iceberg roses grow in clusters, the new buds will be very close to the dead flowers. In the colder climates, do not prune too late in the summer. It will only make more growth, and you do not want it now.
In warmer climates, you will need to do pruning in the winter as well. In late November or early December, cut them back to about 2 feet high if you want shrubs and 3 to 4 feet high if you want taller bushes. Always prune with the shape of the plant in mind.