If a rhododendron is not producing flower buds, it can be a number of problems. Typically, the two most common problems are not enough sun or the wrong nutrients.

Most rhododendrons like "high shade". Hence, if the shade is caused by trees, removing the lower branches of the trees is a good solution. Of course, if the tree is like a Norway Maple, then moving is the only solution.

Fertilizing or not fertilizing can both be problems. Too much nitrogen promotes leaf and branch growth and discourages flower bud production. It can also force late season growth that gets killed or stunted by frost damage. Phosphorus promotes flower bud production and hardiness. Phosphorus can be applied anytime and is slow to reach the roots. So it is good to apply phosphate fertilizers now for next spring. Potassium is necessary for well being. Of course, the soil needs to be acidic for the fertilizers to do any good.

Good Luck!

"Phosphorus is used in the plant in several ways. However, the high energy organic complexes, ATP (Adenosine triphosphate) and ADP (adenosine diphosphate), provide the energy for several chemical reactions within the plant. A phosphorus deficiency, even though very mild, will reduce this energy transfer system and slow growth functions of the plant. It is therefore very important to supply the proper amount of phosphorus. However, excess phosphorus is equally detrimental to plant growth. Excess phosphorus combines with calcium, iron and other micronutrients to form insoluble complexes of these elements. Thus, excess phosphorus generally is observed as stunting and deficiencies of several micronutrients. Phosphorus is normally found in plant tissues at only about one-tenth to one-eighth the level of nitrogen, comprising 0.14 percent to 0.32 percent of the dry weight of leaves."

--Establishment and Maintenance of Landscape Plants, Carl E. Whitcomb

Things seldom happen in isolation, piling it on might have other deleterious effects besides poisoning the rhododendron directly.

"If phosphorus levels are too high, however, the roots do not exude the organic acids and mycorrhizal
connections do not form. This forces the plant to put more resources into root growth to compensate for
the lack of mycorrhizae. So in a sense phosphorus will increase root growth – but at an added cost to the
plant. The resources expended by the plant in growing additional roots to take the place of mycorrhizae
are not available for other plant needs.
Shrub and tree species that are mycorrhizae-dependent have a difficult time surviving in soils where
mycorrhizae cannot develop. In particular, seedlings and newly transplanted materials are less efficient in
absorbing water and minerals from the soil and are more likely to suffer transplant shock than plants
where mycorrhizae are present. Adding mycorrhizal spores to soils where phosphorus is too high is
ineffective – the spores will remain dormant"

The low 20's is as cold as it has gotten since I have lived here, and that is fairly unusual. A USDA site puts me in zone 7 or 8, but another one says 8 or 9, which makes more sense, I think. We do have very hot summers....90's and about 10 days over 100, but that doesn't seem to bother my other Rhody and 3 azalias. Maybe I just need to keep my fingers crossed more and I will reevaluate the fertilizer, which as I said has been just top dressings of compost. Thanks again! Wobur