Rhododendrons and azaleas need a fertilizer with organic nitrogen, and phosphorus and iron. The organic nitrogen is to avoid killing the mycorrhiza that live symbiotically in the soil with the roots helping make phosphorus available to the roots of rhododendron and azaleas.

These plants also need acidic soil. The best way to acidify soil is with powdered sulfur, never aluminum sulfate which will eventually plants like rhododendrons and azaleas. Also avoid areas near concrete and mortar, especially fairly new construction. The lime in concrete and mortar reduces the acidity and may make the soil basic (opposite of acidic).

These plants also do not like salt, so you need to avoid being near or get run-off from areas which are salted in the winter like walkways and streets.

The best fertilizer I know of is HollyTone, which uses Feather Meal for nitrogen and also has sulfur. I also use Super Phosphate since my soil is very low in phosphorus. I also add additional sulfur since my soil isn't quite acidic enough for all of my rhododendrons.

In any case I would only apply at half the rate on the package and only apply once a year near bloom time in the spring. Besides lawn fertilizers, the water soluble Miracid and Miracle-Gro products are among the worst things one can use. They are water soluble salts that only have a temporary effect and are harmful to the soil.

If a plant needs nitrogen, the leaves will be uniformly yellowish. A good fertilizer like Holly-tone should be able to help that. It will take time, but will eventually help.

If the leaves are yellowish with green veins, then the plant is chlorotic. This can be a lack of acidity in the soil and/or a lack of iron, phosphorus, and/or magnesium. Iron sulfate is a good source of iron. Super Phosphate is a good source of phosphorus. Epsom Salts is a good source of magnesium. And sulfur is the best way to acidify soil, but it is slow and long lasting.

Holly-tone Label

A newer product that may be good is:

Whiteny Farms Natural Azalea, Camelia & Rhododendron Food

It doesn't appear to have sulfur in it, so you may need to add sulfur.

Thanks for the clarification. I hadn't applied Holly-tone in a couple of years - did so earlier this spring.

While I've never had my soil tested, I believe the PH is fine as my only mulch is that of oak leaves (years and years worth).

Nothing like a little 'nitrogen boost' as we received from that 3"+ nor'easter last nite. Gardens which have been looking better from the date of my initial post are looking much better at this time (no amount of watering from garden hoses can make up for the nutrients in good ol' rain water).

Thanks again.

And if that storm system came with lots of lightning, your plants (ALL plants) received a large infusion of 'fixed' atmospheric nitrogen.