Rhododendron flower buds are very distinctive - large and shaped like a tight pine cone or the dome of a Russian Orthodox church. (Azalea buds are similar, but usually smaller) Deer absolutely love them, so that may be your problem. Notched leaves usually indicate damage from vine weevils, but may also be from deer. Lots of high winds with low temperatures last winter in the northeast led to a great deal of winterburn. Nova Zembla is rated as very hardy, but in my experience suffers from windburn more than many other varieties. Gibraltar is a deciduous azalea so loses its leaves each fall even though it sets flower buds at that time. If you see evidence of deer eating them, that's the most likely reason the buds have been lost. Phosphorous is unlikely to do any good unless a soil test shows a need. A light application of Hollytone or another complete fertilizer made for acid loving plants may help the plants grow. The number one reason for problems with rhododendrons is failure to loosen the rootball when planting and/or failing to make sure the rootball is sufficiently damp. If you put them directly into the ground without doing these things, it's easy enough to dig them up and replant. There are spray products which allegedly (I'm pretty much a skeptic when it comes to hungry deer) protect plants from them.

maybe if i had seen this in march... evergreen azalea season is pretty much over down here. i do have some late ones just now starting but not really a "display" as they are scattered about as single-late specimens in groups with other shade perennials. if you like these plants, places like bellingrath gardens, calloway gardens and other deep south public gardens are spectacular during azalea season.

Rather than mounding, mulch them. Mulch is placed over the roots but not touching the main stem (trunk). Rhododendrons and azaleas have a fine, hair-like root system that grows outward on the top 2-3 inches of soil. Since the roots are so shallow, any cultivating or pulling roots out will disturb the roots. They like moist, but well drained soil with lots of organic matter and a good dressing of mulch. Soil around the rhododendron's shallow roots must be kept cool. To keep the soil weed free, cool and moist, mulch it with a 2-3 inch layer of an airy organic material such as shredded leaves, leaf mold, pine needles, or pine bark mulch. Don't use shredded hardwood mulch since it often drives the pH upward. Pine bark is especially useful since it can lower the pH where it is too high, but it is best used on relatively flat ground since it's light in weight and tends to float away in heavy rain. [Sketch courtesy of Harold Greer] Rhododendrons do best when they have about a 2" to 3" layer of mulch to hold in moisture, prevent weeds, and keep the roots cool. Since most mulches are organic, they need to be topped off periodically, usually about every year or two. Do not make the mulch over 3" thick. Keep the mulch about 2" to 3" back from the trunk/stem of the plants to avoid bark split, collar rot, and rodent damage. It is best to mulch with a 2-3 inch layer of an airy organic material such as conifer wood chips, ground bark, pine needles, pine bark or rotted oak leaves. A year-round mulch will also provide natural nutrients and will help keep the soil cool and moist.

It is best to limit azalea feeding to before bloom (like you did) and after bloom, but light feeding is best unless the plants show symptoms of malnutrition. Besides shade and drought there are many other concerns: 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. * 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. * 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. If in fact you see buds that died and never formed flowers, that may be caused by several problems: * Bud blast. Disease may attack the buds before they open. If it is a fungal infection, the dead bud will be covered with short hair-like structures. * Fall Blooming. Some causes of fall blooming include a dry summer and moist fall and/or warmer climates including a warm fall. For some reason, fall blooming is more common in Georgia according to Dr. Sandra McDonald. Plants which are not sufficiently hardened off or are exposed to unseasonable warm spells can start bloom prematurely. These blooms are seldom satisfactory and many times get frozen before opening fully. In any case, the seasonal bloom is lost. Avoid application of nitrogen after late spring, but phosphorus and potassium may be applied throughout the growing season. Application of nitrogen too late in the season can hinder hardening off in the fall. * Low temperatures. The buds could be flower buds that froze. Early frosts are especially distructive. Plants harden off progressively in the fall. If a frost occurs before hardening is complete, the frost can kill flower buds. Late frosts in the spring after dormancy is broken is also a problem. This is expecially true of early bloomers such as PJM that break dormancy very early. Cold climates may be too cold for many rhododendrons. Most rhododendrons have a low temperature at which the flower buds are damaged and will not produce flowers. It varies greatly from variety to variety and somewhat from season to season. Flower buds can also be damaged by cold, dry winds, particularly when warm winter weather is followed by a period of bitter cold. * Nutrients. Improper nutrients my be a problem that affects cold hardiness and flower bud set. A few things you can do are to fertilize with phosphorus (super-phosphate) per directions to increase hardiness and flower bud set. This can be done any time. Do not use nitrogen rich fertilizers as they may inhibit flower bud production and also reduce cold hardiness. Lawn fertilizers are notoriously high in nitrogen and should be kept away from flowering plants. * Acidity. Measure the pH and acidify if necessary. Flowers of sulfur (powdered sulfur) or iron sulfate are the best chemicals to use to increase the acidity [lower the pH]. Do not use aluminum sulfate since aluminum salts build up in the soil and eventually becomes toxic to many plants including rhododendrons and azaleas. If soil is too acid, the symptoms can be the same. Very acidic soil can prevent the roots from taking up nutrients. As many of my rhododendrons are planted in very acidic forest soil, an application of Dolomite and a light topdressing of mushroom manure in late spring is all they need. Sprinkle the lime on in late winter, very early spring. Don't overdo it - just a light sprinkle. If it is mid-spring, get the lime on right away so the rhododendron roots will be able to take up the soil nutrients in time for new growth. If you don't have rain, water it in well. * Protection. If the plants are wrapped in burlap during the winter, they may gain a few more degrees in hardiness. * Drought. When soil moisture is too low, the buds will not open. Watering will usually resolve this condition if detected soon enough. Also, summer drought with a moist fall can contribute to fall blooming. * Deer Damage. Deer and rabbits may eat many of the flower buds as they browse in the winter, particularly if the weather is harsh and other food is scarce. Here is a link that might be useful: How to grow rhododendrons and azaleas.