The new growth on my old azaleas shoots straight for many inches, and then forms about five straight branches at the end, in a star shape. The old growth is dense and attractively gnarled. I’ve been cutting off the new growth, because it is so ugly. How to I encourage more attractive growth? The shrubs are not fertilized, and get only some chopped-leaf mulch.
Here is a link to Margaret’s pruning faq’s. The pruning faq’s contain all the pruning basics, such as what time of year to prune and where to make cuts.
The new growth on your azaleas is growing straight in order to reach more light for the leaves and flowers which will grow on the fire-work like arrangement of branches at the top. This growth pattern suggests that the interior of your azalea is too over-crowded. This is preventing the plant from renewing itself in its current shape, instead it is trying to grow a whole new layer above the old growth. Make sure there are no dead branches in the interior of the plant (this can be quite a task if you have not pruned out any dead wood in a few years.) If your azalea is deciduous you may find it difficult to determine what is dead during the late winter/early spring pruning season. In this case you can wait until the plant has leafed out as pruning out dead-wood can be done at any time of year. If pruning out the dead-wood still leaves the interior looking congested, you should prune out some of the oldest least healthy looking wood in the congested places. Just be careful not to prune out more than one-third live wood in one year. For the long-term health of your shrub it is important to not cut out all new growth. As the branches grow older they become more susceptible to disease and insect damage, so they need to be slowly replaced with new healthy growth. This is how woody plants are able to live for such a long time. It is sometimes difficult for us to let go of a particularly lovely growth pattern of a shrub, but it is important to remember that the shrub is a living being and needs to change over-time (just like us). Trust that once there are appropriate light levels falling on the new buds at the base of the plant the new growth will be as enchanting as the old.