If you go back to the parents of the hybrid Hotei, you find the species wardii, one of the few species with yellow flowers. Because of this color characteristic, wardii is present to a greater or lesser degree in a large number of yellow hybrids. Unfortunately, along with the yellow color, wardii has also contributed a high degree of susceptibility to a number of fungal root diseases. These diseases are much more of a problem in areas with high summer temperatures, especially soil temperatures, than in more moderate areas such as the UK, the PNW and New England costal areas.

Grafting is a much more common means of propagation in Europe than in the US, but if some of these yellow hybrids were grafted on to disease resistant root stock like Cunningham's White, they would very likely do well in areas where they are currently ungrowable.

For what it's worth, I've found Goldkrone and Capistrano (so far) to be very reliable true yellows in coastal Maine as long as winter temperatures do not go below -5.

Hi mainegrower,

When I find a nice specimen of Capistrano I'll give it a try.

I have no doubt that rhodyman's comments regarding Capistrano are accurate for his area and that the same warnings should apply to the OP's Philadelphia area. Here in a cooler coastal Maine, however, Capistrano does not seem to exhibit the same problems. I have had no difficulties with my own in 5 years and the owner of one of northern New England's largest rhododendron nurseries has had no extreme problems with either his own plants or those he's sold to many customers.

From Rare Find Nursery, re Capistrano: "For plant masochists only!! This has been a cranky grower for us, requiring excellent drainage."

Unfortunately, My Jane (I have three in different locations) is acting the same way in my garden, which was one of Hank's favorite yellows.

However, I AM a plant masochist, so will wind up getting Capistrano, especially if I see them at Ronny's Nursery Delaware again, $29 in 3 gallon containers.

I like what I see so far with evening glow, which blooms in June for me.

Supposedly all yellow Rhododendrons require excellent drainage and cool roots to prevent phytopthora. There are some efforts to use R. hyperythrum to breed this trait out. I haven't heard of any successes yet.

The Europeans graft their yellows onto disease resistant stock and escape problems with phytopthora and other soil problems.

About five years ago I purchased a B&B Mary Belle that looked like it had suffered from drought. Pretty beat up. Got it cheap, no guarantee. I had wanted Mary Belle since reading about it in Baldsiefen catalog in the late 70's, so I jumped at the chance. It has since become a 4x4 beautiful rhodo, outperforming itself year after year. To my eye I see some subtle yellow.
At this point, seeking yellow in my woodland, when I lose a yellow elepidote, I replace with either a deciduous azalea, or a lepidote; not going to bother too much anymore with the yellow elepidotes.
Once, during a golfcart trip to the late Hank Shannan's woodland, he picked out this yellow lepidote. It wasn't labeled and he said he wasn't sure what it was. I have since come to think it might be 'Hank's Mellow Yellow'
Really nice shade with a hint of green.
Photos are Mary Belle top (unfortunatly the only photo I have; doesn't show the color well), HankâÂÂs Mellow Yellow? below (my beautiful Lenape next to it)

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I had Evening Glow. I planted it in a south facing bed. It suffered horribly from Lace Bug. I moved it to a north facing bed and the Lace Bug problem went away, but the plant didn't do well and eventually died. I never got more than a couple blooms. It is a pale yellow.

I saw the Ted Van Veen who had introduced this plant at his nursery in Portland, Oregon. I told him that unfortunately the only thing that was yellow was the leaves. It is a great West Coast plant but have yet to see any examples of it doing well on the East Coast.

I got three very small Evening Glows and a three Autumn Golds from Van Veen 26 years ago. It was late in the spring and I was taking a risk, admittedly. I lost four of the six. Probably in each case it was my fault for putting them in a poorly drained bed. One of each variety is still alive -- the one that I planted on my shady hillside.

Evening Glow is probably in shade that is too deep of shade as it has gotten rather leggy. My surviving Autumn Gold is shaded by a row of tall American arborvitae after noon, and by my house much of the morning. It has been absolutely spectacular most years, though in 2014 I lost 90% of the bloom to an exceptionally cold winter.

It's deep pink in the bud, opening to a riot of pink, yellow and cream, fading almost to white. It's not a true yellow, but no one cares as the plant in full bloom is a show stopper.

This is in northern Virginia, inside the Beltway, with heat and humidity to beat anything Philadelphia can offer. It may help that I use a great deal of rough mulch on these rhododendrons. It comes mainly in the form of yard waste that neighbors throw out, such as sago palm trimmings, pine boughs and the seed pods from sweet gum trees.

Thanks Woodside that is an interesting report. I'm not surprised your yellows only survived on slopes. In retrospect, if I'd wanted to focus on rhodies, I would have sought out a property that somewhat steeply slopes - preferably to the north. Because those are the two factors causing water mould rot: high soil temp and lack of aeration due to water ponding or not quickly draining. My R. rex was doing fine in the summer of 2011, which was hot, until almost 40 inches of rain fell in roughly 40 days around hurricane Irene. The soil was permanently wet and I'm lucky I didn't lose even more Ericaceae. The soils north of Baltimore slowly become loamier clay rather than red brick clay so that might have helped a bit. In fact after rains a bizarre slurping sound can be heard as air is sucked back into these soils.

Do your neighbors have mature outdoor sago palms (?) LOL. I guess not although there is one Chinese species that is borderline hardy in DC.

I have an 'Evening Glow' but I didn't plant it in a great spot - I have a paucity of slopes - and it hasn't flourished. Although it shows no obvious signs of dieback either. I'd rather have a plant sulk than do what Capistrano did, which was grow like crazy for 5 years and then die in 2 weeks after a period of heavy summer rain. (if I'd known better in 2006, I would have planted it on a huge mound and it would probably still be around. It's a wan yellow but overall a pleasant looking plant) 'Evening Glow' is a high priority plant for grafting onto root rot resistant rootstocks, although my grafting skills have a long way to go.

This post was edited by davidrt28 on Thu, Sep 25, 14 at 13:16

I have a couple of yellow rhododendrons, Yellow Hammer and Butterfly. Both are doing fine after 25 years, but could use some more sun. I will move the Yellow Hammer this fall in to a more desirable spot.
Growing rhododendrons here is easy. The hard part for me is, that after 30 some years, they need a lot of pruning. Initially I didn't give them enough room. I don't mean so that after all this time they stand in the garden as individual plants, but have them growing as a tall groundcover under upright Japanese palmatums and japonicas. In a lot of cases they're squeezing each other out to the point of death. It's all I can do to save some by judicious pruning or moving them.
If only I knew then, what I know now........
Time and the Internet have been a great help.
Mike
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Capistrano and Goldkrone continue to do well for me. I've found Lemon Dream and the species keiskei to also be reliable true yellows. It has some pink in the flower, but Jenny Tabol - usually available at Rarefind - is another good yellow. Hello Dolly has both orange and pink as well as yellow in the flower and is somewhat sprawly in growth, but it's been reliable for me for 25+ years. Haven't grown them long enough to be certain, but Bernstein and Festivo look good, too.

"Unfortunately, My Jane (I have three in different locations) is acting the same way in my garden, which was one of Hank's favorite yellows. "

I'm still having good luck with 'My Jane'. In fact I had one that was in too low a spot and showing some dieback. I moved it on to the top of a mound of soil and cut away the dead bits. I experimentally did _not_ give it antifungal treatment, since I already have another My Jane in a totally different part of the garden that is fine. Well, that plant recovered very well. Just with the re-siting. So I would say for a yellow it is very tough. It's a better yellow than Capistrano, but only by a little bit. OTOH Jenny Tabol is a notch more saturated, and though some wouldn't like the pinkish edges, I think they help bring out the color. OTOOH, (on the other other hand...) Nancy Evans is WAY more saturated. But I protected my NE with antifungals for 2 years. It was planted on a mound. It is a gorgeous plant in and out of bloom, because the foliage is really nice too. When I stopped treatments, it quickly died. So its root rot resistance in a climate with nights warmer than 60F is virtually nil.

One more good one is 'Yates Treena'. To me, slightly better than 'My Jane' but again nowhere near as good as Nancy Evans. So far so good with the root rot resistance. In fact the plant is so vigorous it worries me a little bit, because Capistrano was very vigorous before dying too. Also many of my rhodies are crowded and it will have to be moved soon, which will stress it a bit but give me a chance to reset any circling roots if those are a problem. If I had known in 2006 that I would have been so captivated by rhodies, I would have immediately started planting more high shade. Alas it took about 4-5 years before I realized I had a rhododendron problem haha.

One more thing...here is my ranking from best to least yellow:

Nancy Evans (only 7b but that's probably ok for me)
Evening Glow
Karalee - saw it at Rarefind years ago, next to some My Janes. Not east coast hardy, not sure why Hank bought some. To cross I suppose.
Jenny Tabol - Yates Treena about the same
My Jane
Capistrano
from having seen it at Rarefind: Ivory Max X Sunspray - as light a yellow before you'd have to call it cream or something. But the plant is probably very tough and I have one.