Pruning Deciduous Azaleas:
Some professional gardeners suggest cutting back deciduous azaleas to six or nine inches from the ground, a practice sometimes referred to as ‘bush-whacking’ or ‘hat-racking’. This somewhat drastic methodology can occasionally be seen in the gardens of large estates and is probably a result of insufficient staff being available to do the job in the way it would have been done in times gone by. Some deciduous azaleas will tolerate this practice, however, this approach should be avoided, particularly with older plants, as the shock caused may well result in a number failing to regenerate. And, this is not the way to treat plants that provide you with a spectacular show each Spring. But there are other aspects to consider.
Many older deciduous azalea cultivars are difficult to replace and need to be treated with care. Some, such as the Ghent and Mollis types, have only been sporadically propagated during the past fifty years and certain varieties are no longer in commerce. But many of the ‘lost’ varieties may still be extant in older gardens. A significant number of these plants were imported from nurseries in Belgium and Holland, who tended to supply grafted plants with R.luteum rootstock. In practice the R.luteum component is far more vigorous than the grafted hybrid and will tend to send out new growth from the rootstock of a drastically pruned plant, then it will take over and kill what remains of the grafted hybrid. For this reason it is important before pruning older plants to look at them at flowering time and see if they have the very fragrant largish yellow flowers of R.luteum mixed in with those of the hybrid. Any yellow flowered stems should be completely cut out, taking care not to inadvertently remove any of the hybrid material in the process.
It is also well worth remembering that you will have little, if any, control on the number and direction of the new shoots sent out from the base of plants which have been ‘bush-whacked’. It can take around five years for the plant to reach waist height, and a good many years longer to reach full size. It is also difficult and time-consuming to achieve a nicely shaped bush after it has been drastically pruned. But a more important consideration, that many people only realise after the damage has been done, is that it is likely to be two or three years before the plant will begin to flower again, and a further couple of years before it flowers well. It is far better to carry out the pruning in stages and we will return to this subject shortly.
Inevitably, there are exceptions to most rules, so let’s get this one dealt with now. Should it be necessary to transplant a deciduous azalea, and it turns out to have a poor root system when it is dug up, then after the plant has been relocated cut the branches back to one third of their length to compensate for the lack of roots. Plants cut back in this way generally produce flower buds after the second season.
An entirely different approach to the pruning of deciduous azaleas is well worth serious consideration. Why leave pruning until the task becomes an absolute necessity, then have to face cutting off large limbs from plants that are often not easy to replace or propagate? A much better approach is to take a step backwards, decide which branches need to be removed, then air-layer them instead of cutting them off. Carry out the air-layering at a position on the limb which will produce a reasonable sized new plant, say 18 to 24 inches in length, when the branch is removed at a later date. Some larger branches may well accommodate two layers. Do this in the early-Spring of year one, as this timing provides the plant with a complete season’s growth-cycle, and carefully inspect the success of the layering in the Autumn of year two. Bear in mind that some difficult to root plants, such as some of the Ghent varieties, may require another growth season to develop an adequate root system. Cut off the branch when rooting is complete and plant in a container that is sufficiently large to accommodate a small diagonal cross-stake to give support to the new plant. Grow on for a year in a sheltered position prior to potting out. This is an easy method of propagating. It works well in practice and provides good-sized plants for very little outlay in time or resources. Once again, patience is the key!