Actually rhododendrons and azaleas have adventitious buds under the bark. When a combination of circumstances such as less leaf area and more light occur which could indicate damage to the plant, frequently these buds develop quickly and form new stems.

I assume you are concerned about flower buds. They typically form during the summer and few form in the late summer. However, many buds that are small and look like foliage buds may continue to develop and actually be flower buds. You may be surprised to find that many small buds eventually become large flower buds.

My soil is deficient in phosphorus which is necessary for good flower bud set. For flower bud production and hardiness, super phosphate is a good way to compensate for this. Around the base of each plant I use a tablespoon of dry sulfur and a tablespoon of dry super phosphate when a plant shows signs of problems. For a general fertilizer for rhododendrons and azaleas, Holly-tone is preferred by many growers. It is an organic 4-6-4 fertilizer with powdered sulfur, minor elements such as magnesium, iron and calcium, and trace elements also. (The Miracle-Gro pelatized slow-release azalea and rhododendron product is OK.) When fertilizing only fertilize once in the spring and at half the rate on the package. Some people fertilize once before blooming and once after blooming, but only fertilize at half the rate on the package. Some nitrogen in the spring will help flower bud set. Too much nitrogen and nitrogen applied in summer or later will promote vegetative growth which can get frozen back.

Rhododendrons require phosphorus, as well as nitrogen, and adequate sunlight to produce flower buds. Not always understood is the length of time required for phosphorus to reach the root system and be taken up by the plant. As long as six months may be necessary for this process. Rhododendrons which have formed few, if any, flower buds by fall should receive an application of granular phosphate some time during the winter to assure flower bud development during the following summer months. No need to be concerned about applying too much; a rhododendron is not a phosphorus glutton. It will feed on no more than required.

Some areas of the west coast actually have a pH that is too low, too acidic. In those areas some dolomitic limestone can help flower bud set. Most authoritative books and articles state that rhododendrons are acid lovers. However a pH of 5.5 to 6.5 is optimum. A wide selection of the native species originating in Asia grow in mountains of dolomite limestone where the pH reading approximates 6.0. The addition of dolomite, which is a combination of magnesium carbonate and calcium carbonate, to plantings darkens foliage color and increases flower buds. Gypsum, the common name for calcium sulphate, is another type of fertilizer some gardeners seem to use successfully to improve the flower bud set.

High temperatures and/or drought may also affect flower bud development. Plants may drop flower buds when stressed.