It appears to have departed it's mortal shell and gone to Ericacea heaven.

This post was edited by dbarron on Sat, Aug 30, 14 at 9:50

It's dead.
BTW it really wasn't that dry a summer in the DC area.
See my post here:

Here is a link that might be useful: http://forums.gardenweb.com/forums/load/azalea/msg091739277896.html

In Virginia and DC it is difficult to keep some rhododendrons alive in the summer. Drought can cause dieback and hot-wet conditions cause root rot. Root rot is almost always fatal. Dieback can be survived. I think you have root rot.

Phytophthora Root Rot, Phytophthora cinnamomi: This is a serious, widespread and difficult-to-control oomycete, or water mold, affecting a wide range of plants . The symptoms of Phytophthora root rot vary with the cultivar. Some cultivars fail to grow or grow very slowly with pale green foliage and may die after several years. Others suddenly wilt and die within a few weeks. Roots are reddish-brown, brittle and often limited to the upper portion of the media in a container or very close to the soil surface (upper 2 inches). The reddish-brown discoloration advances to the larger roots and eventually to the lower part of the main stem. Phytophthora root rot is favored by high soil moisture and warm soil temperatures. The disease does not occur as frequently and may not be as severe on well-drained sandy soils as in heavy clays or poorly drained soils, etc. The disease is common and severe in areas where run-off water, rainwater from roofs, etc. collects around plant roots. Setting woody plants deeper than the soil level in the nursery or container, over-watering plants, or long periods of heavy rain also favor disease develop especially in shallow soils with underlying rock or compacted hard pans. Phytophthora root rot must be prevented as chemicals are often ineffective in controlling this disease after above ground symptoms appear.

I am in SE PA and just planted a rhododendron bed in a moist area with an artesian well coming up. I used raised beds. I didn't dig holes at all, I just put down a bag of peat humous for each plant and planted in the peat humous and mulched thoroughly with pine bark. In the south they use plants with R hyperythrum in their pedigree. One such group I use are the Southgate series of R. hyperythrum hybrids by Dr. John Thornton of Franklinton, LA.

Here is a link that might be useful: Rhododendrons for sun and heat

Shoot...sounds like it's a goner. I noticed a woody, tumorous sort of growth at the base of the plant just above ground level a couple weeks after planting it. Is that a sign of the root rot you described? It seemed to be doing well and then this happened. Now all the leaves are brown and crispy. Should i dig down to the roots and look for the reddish brown coloration to confirm root rot?

It's hard to say about the "tumor". Could have been an old circled root or something.

As for diagnosing root rot by root inspection, there's really no need although you can if you want. The problem is they can be dying before anything is visible, and after they are dead other, non-pathogentic decay organisms will quickly turn them some color anyhow. So seeing the root look a certain way probably isn't truly diagnostic...you really need to be, IMHO a plant pathologist to really know that a _root_ is dying of a water mold/phytophthora. OTOH, you don't need to be one to know the _plant_ is dying of that. The picture you posted is the classic presentation of a plant dead from root rot.

BTW when the Maryland Department of Environment tests plants for Sudden Oak Death, the most serious root rot/water mold, they do a PCR screening (DNA amplification) that is thousands of times more sensitive than any unmagnified visual observations could possibly be.

If I were a non-specialist gardener in the DC or anywhere south area - so that means all of Piedmont VA - and I just wanted a pleasant pink blob when is what most people think of w/rhododendrons, I would definitely only plant the "Southgate" series, or the equivalent R. hyperythrum hybrids like 'Opal Thornton' or 'Charles Loomis' which you can sometimes get at Rarefind.

BTW in addition to Rhodyman's excellent write up...I would say from my experience that a given variety probably becomes less -likely to be struck by- root rot as it ages into the landscape and becomes more mature, but not more -resistant-. There is a difference. In other words for some varities, stress triggers it, like under/over watering in a hot summer climate. As a plant becomes more fully established it becomes less able to be under/over watered...but never impossible to do so. This explains why my 'Capistrano', which had been the best and biggest rhodo in my garden, died almost overnight when we had a exceptionally wet and hot period in mid-summer 2012, as I seem to recall. After a dry period. It was at least 3' tall and very full, and had never had signs of illness before.
OTOH, I had a 'Jenny Tabol' - which is a better yellow in my opinion anyhow - that came very close to dying of root rot. I treated it with a fungicide whose exact formulation is no longer even available so there's no point to mentioning it. I also lifted it, replanted it a few inches higher, and cut all the diseased foliage and stems back. Also moved an Ilex in position just south of it to shelter it from the sun...currently shaded by a junk tree whose branches I'm slowly removing. It is doing fine now. Some people would think "oh dear, the plant's soil is still carrying the root rot, you should remove it and never plant another rhododendron there" but that isn't the problem. The root rot was in the soil all along. The plant's stress weakened it, allowing it to become completely infected. I removed the source of the stress and the plant was able to recover. (I even recall watering with ice cubes to lower the soil temp during the 'critical condition - life support' period!) So, the plant will continue to be healthy and grow until a more severe stress again weakens it. All this being said, it is generally not recommended to try to save dying plants by these methods. I've only had it work once out of about 4 times.

This post was edited by davidrt28 on Mon, Oct 6, 14 at 15:01

And btw as I've posted several times before here, the true long term solution for these cool-summer varities is either:
breed heat resistant yellows (a very long way off in my opinion)
or graft onto varities resistant to root rot

I'm doing some experiments with grafting and the 2 that look like they might be taking are:
Nancy Evans on Charles Loomis
and
Jenny Tabol on Cunningham's White

Interestingly, CW calluses up very quickly and noticeably. The question is whether the callus is truly a fusion with the JT. It will be a while before I can know that the graft took. But the fact it calluses so quickly might be a reason that variety was used for understock so extensively in Europe.
(also possibly because its tendency to dwarf was considered desirable in smaller gardens there)

(Sorry original poster, this is probably no longer of interest to you.)

Wow, I Just found this excellent article.
One concern he raises, which I've had myself about the combined grafting/rooting system used in Europe and finally by some nurseries in the US, is whether it might let scion roots slowly try to overgrow the understock. Which would be bad. You see, in Europe they might just need the under stock during the first few years of the plant's life anyhow. They aren't using rootstocks there to fight root rots except in the context of avoiding amateur gardener mistakes. Grafting merely helps sell a plant that will be a little easier to establish. ( Or if it's for calcareous soil, there is constant selection pressure again the scion.) Here on the US east coast we will go on having stiffling hot summers with single downpours sometimes dumping more rain in 2 days than NW Europe gets in their entire summer. (I had a 2 day, 14 inch downpour a few years ago that killed a rare alpine Eucalyptus that had been incredibly winter hardy) So we need the understock to be the understock for good.

Here is a link that might be useful: http://scholar.lib.vt.edu/ejournals/JARS/v48n2/v48n2-bondira.htm