Failure to set flower buds may be a sign of too much health and vigor in a plant. One solution my be to prune the roots by cutting around the plant with a spade or moving the plant. This will check foliage growth and encourage production of flower buds. Application of nitrogen rich fertilizers are the main cause of vigor which suppresses flower bud production. Deadheading flowers as soon as they wilt can promote flower bud production. Too much shade, a cool wet summer, or inadequate phosphorus or potassium in the soil may also suppress flower bud production. There are a number of other reasons for a lack of flowers. The effect of each variable depends upon the variety of the plant. The effects include:

* Pruning. The buds are formed in late summer and early fall so pruning then or later is not advisable since it will remove flower buds. New leaf buds will form in the spring, but new flower buds won't form until the next year.

* Variety. Some plants will never bloom. Some rhododendrons that come from the seed of a hybrid plant will look good but will never produce flowers or will produce very poor flowers. To come true to the parent plant, a hybrid may be propagated by cuttings or tissue culture but not from seed. A good hybrid seedling only comes about once in a while. For that reason it is important to know that you are getting a good named variety or a good species.

* Fertilizing. 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. Potassium is necessary for well being.

* Weather. Cold weather can kill flower buds. Usually you see the brown buds in the spring. Cold spells in the fall or spring can damage buds that are not hardened off. Bud blast (blooming in fall or winter) uses up good buds which are then not available at the normal blooming time.

* Age. Most rhododendrons take 2 to 3 years to bloom from a rooted cutting unless forced. Some take longer and some bloom sooner. From seeds the plant may take 1 or 2 additional years.

* Sun & Shade. Some rhododendrons need full sun to bloom and others can take fairly dense shade. In general, the more sun the more flower buds but also the greater exposure to damage from desiccation in summer or winter. More shade produces tall spindly foliage and less flowers.

* Inspection. You can usually tell if the plant has ever bloomed. A rhododendron that has bloomed will have the seed pods on it unless it has been dead-headed. If dead-headed too late after blooming, new flower buds can be damaged.

There are many other cultural variables that influence the plant's health and hence, its ability to produce flowers.

Here is a link that might be useful: How to grow rhododendrons and azaleas.

Is there a list someplace of how much sun different varieties need? I have a Taurus in shade that bloomed last year, but not this year, and a Sir Charles Lemon in half shade that has never bloomed for me. They're my only ones, so I can't say that others are doing better; but it sure seems that every other rhodie in the neighborhood is going gangbusters, so I don't think I can blame the weather. I don't fertilize except with compost (regular vegatable stuff compost, not a manure), so that's not it. The Taurus does look a bit chlorotic, but they're supposed to be acid lovers, so I wouldn't guess iron would be a problem. Maybe your link will tell me.

I will go check your link too.

Looking chlorotic indicates they either need iron or acidity to make iron available. Sometimes phosphate helps promote blooming. I always use superphosphate and sulfur when I fertilize. But I only fertilize about every 10 years.

Jennie, unless planted near an area of lawn that is limed regularly, or near newish construction with cement foundation that is leaching lime, most soils in W WA support the needed acidity for rhododendron quite well.

There are other reasons for a chlorotic appearance than just acidity though - anything that would damage or suppress healthy roots can cause chlorosis. Planting the rhododendron too deeply so that the fine network of surface roots are unable to function properly, poor drainage, compacted soils, weevil larvae (but here you would surely notice leaves chewed by the adults) to name a few. You did mention you don't fertilize, but fertilize burn (roots) is another.

As for the sun, I'm not growing Taurus here but I 'visit' one regularly further inland (Longview area) and it's growing in almost full sun. In the worst soil imaginable, blue-gray clay with a musty unpleasant smell, and bad drainage over winter. Has deep green leaves, large and abundant trusses every year and I've never been able to figure out why :)

So maybe the Taurus needs more sun, if it's happy in full sun here. So I should check on how to transplant it, much easier than moving the four or five big cedars shading it....