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Rhododendron Bloom in Full Shade?

Posted by mistascott 7 (My Page) on
Fri, Mar 18, 11 at 17:11

I have a new Northern Starburst (first member of Genesis Series of improved polyploid PJMs) Rhododendron. I have a spot that does not receive any direct sunlight as it sits in front of a 4 ft. brick wall. I also have two alternate locations that receive either morning or evening sun.

I have read that these will bloom in full shade since they do not use energy producing seeds. I have also heard that the Northern Starburst prefers (or is it tolerates?) more sun that most Rhododendrons and that blooms and fall foliage color will suffer in full shade.

Does anyone have experience with rhododendrons generally in full shade or PJMs/Northern Starburst in particular and care to give some advice?

Thanks!


Follow-Up Postings:

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RE: Rhododendron Bloom in Full Shade?

A lot has to do with the quality of the shade. Many rhodendrons will set buds and bloom without direct sun, but none will do well in a location that does not receive a good deal of light, which is not the same as sun.

Excessively shady locations will reduce if not eliminate bloom and encourge leggy growth.

The claim that not setting seed helps this particular variety bloom in shade seems very unlikely to me. Seed set is generally not a problem with any lepidote type rhododendron including all those in the PJM group. Allowing lots of seed pods to develop on elepidote (large leafed) rhododendrons can reduce bud set for the following year, but doesn't have anything to do with light exposure.

The best choice would be morning sun, afternoon shade.


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RE: Rhododendron Bloom in Full Shade?

Thanks for the reply. The garden center claimed that these will bloom even in dense shade. This area gets some light, but not a lot. I may try locating it there for a season and see what the blooms look like next Spring. If they are lackluster, I can always transplant.


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RE: Rhododendron Bloom in Full Shade?

The best rhododendrons for shade are:

'Boule de Neige' means "Ball of Snow" in French. As you might expect, the flowers are white, in perfect rounded trusses, and geometrically proportioned to the leaves. The habit is dome shaped. Leaves are matte green, and the plant's constitution is tough and very hardy. It grows to a height of 4' and width of 5'. It even blooms well in deep shade.

'Bow Bells' is a perfect mound of pink. The flowers are followed by shiny, copper colored new leaves. As the season progresses, the mound becomes a superb jade green with rose-red bud scales for another show of color. While growth at 10 years is 3', it will become a larger plant, so give it enough space. A site with filtered light is best for Bow Bells. Fertilize lightly, as an excess of fertilizer will cause foliage burn more easily than on most rhododendrons.

'Elviira' rhododendron is very hardy. It grows to a height of 2' and width of 18" to 24". It grows well in shade. A very low growing rhododendron cultivar. Densely branched, it is covered with flower buds that are hardy to -30F and open bright red. From the group of Marjatta hybrids developed at the University of Helsinki, Finland.

'King George' is a tall hybrid rhododendron that blooms in mid-spring, producing huge pale pink flower clusters that turn white as they mature. It generally grows 6 feet tall but may reach a height of 12 feet. With rhododendrons, the rule of thumb is that the larger the leaf, the less sun they can handle gracefully. 'King George' and other Loderi rhododendrons are large leaf plants that follow this rule. However, if given enough shade they are also drought tolerant.

'Nova Zembla' rhododendron has true hardiness in a red. A vigorous plant that has good foliage and will grow in more difficult areas. This hybrid exhibits some outstanding characteristics. Of course, hardiness tops the list. A nice looking contrast with other plants. Extremely showy, red flowers make a real display in the spring.. Dark red flowers in a ball-shaped cluster. Broad, bushy plant. Cold and heat tolerant and sun and shade tolerant. It grows to 5' tall and is hardy.

'Ramapo' is a good dwarf rhododendron. It grows approximately 2 feet tall and 4 feet wide. Flowers are bright violet-pink. 'Ramapo' is hardy to -25F. Tolerates sun and shade.

'Red River' is a hybrid of a red flowered maximum. It has the late bloom and the large leaves of maximum. The flowers, larger than maximum's flowers, are bright red with a white throat and small yellow dorsal flare. A robust plant with an upright habit, it can be an open grower, but pinching will help and its habit gets better with age. Good for extending your bloom season into June. 'Red River' is hardy to -20F. Tolerates sun and shade.

'Snowlady' is a hybrid rhododendron that grows to a height of only 30 inches. It produces an abundance of snowy white flowers and has fuzzy green leaves.

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'P.J.M'. hybrid rhododendrons. The 'P.J.M.' group of rhododendrons are smaller, growing to a height of 3 to 5 feet tall. Form is rounded and the foliage is leathery and dark green until fall when it turns almost purplish. One of the reasons the 'P.J.M.' group is such a heavy flowerer is that the plant does not set seed. They are very hardy, among the hardiest and most shade tolerant rhododendrons. They include the following:

'Black Satin' has a semi-erect habit and bears an abundance of showy, vivid, dark rose-pink flowers in mid-April. Fall and winter foliage is glossy and very dark purplish-black.

'Counterpoint' is a deciduous shrub with a spreading, upright habit, and bears an abundance of showy, semi-double, vivid, bright pink flowers in mid-April.

'Desmit' has a dense, mounding habit and bears an abundance of vivid, showy, pink flowers in early April. This cultivar has shown to be moderately resistant to sun scalding.

'Elite' is a vigorous, tall grower and bears an abundance of vivid, showy, rich pink flowers in mid-April.

'Henry's Red' has a broad, upright habit and bears an abundance of showy, vivid, deep red flowers beginning in mid-April.

'Laurie' is a slow grower with a compact habit, bearing an abundance of showy, single to semi-double, very light pink flowers beginning in mid to late April.

'Low Red Frilled' has a spreading, short, compact habit and bears an abundance of showy, frilled, vivid red flowers beginning in mid-April.

'Marathon' is a deciduous cultivar with a semi-erect habit, and bears an abundance of showy, vivid, magenta flowers beginning in mid-April.

'Molly Fordham' has a compact habit and bears an abundance of showy, vivid, white flowers beginning in early May.

'Northern Rose' has a semi-upright habit and bears an abundance of showy, vivid, bright pink flowers beginning in mid-April. This rhododendron is the result of a cross between R. 'Waltham' and R. mucronulatum 'Cornell Pink.' It was first developed by Dr. Robert Ticknor.

'Olga Mezzitt' is a vigorous grower with a spreading, upright habit and bears an abundance of showy, vivid, peach-pink flowers beginning in late April.
'Regal' is a vigorous grower with a broad, spreading habit which bears an abundance of showy, vivid, light purplish-pink flowers beginning in mid-April.

'Victor' is a slow grower with a compact habit and bears an abundance of showy, vivid, light purplish-pink flowers in early April.

'Waltham' has a dense, mounding habit, to 3 feet tall and wide, and bears an abundance of showy, vivid, pink flowers beginning in mid-April. Leaf spotting occurs when exposed to full sun.

'Weston's Pink Diamond' is a semi-evergreen shrub with a spreading, upright habit and bears an abundance of frilled, double, vivid, pink flowers in early April.

'White Angel' is a semi-evergreen shrub with an upright habit and bears an abundance of showy, white flowers, which open from lavender buds, beginning in mid-April.

Here is a link that might be useful: Rhododendrons for Shade


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RE: Rhododendron Bloom in Full Shade?

Great post, rhodyman!


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RE: Rhododendron Bloom in Full Shade?

Rhodyman, your posts and website are wonderful. Thanks for all the trouble you go to for the rest of us.

I'd just like to add that 'Loderi King George' might be a bit iffy in terms of hardiness for a zone 7 grower, though I've always wanted to try it. Its tall progeny, County of York, is plenty hardy, though, and performs really well in bright shade, total shade--no direct sunlight. Ours is located where it peeks up above all the rhododendrons crowding in all around, but it blooms well and reliably every spring, late midseason. We once had one functioning like a star in 3-4 hours of direct sunlight and it did wonderfully well... until it succumbed to what I think was phytophthora root rot. The one in total shade is higher up on the berm with better drainage but also is farther into the deeper shade of deciduous trees so it seems a small miracle that it blooms as well as it does.

I haven't seen 'County of York' available for sale around here for a long time. I hope it's still in commerce. It's easy to grow in a variety of conditions and I like it. Its legginess makes it look good growing in a woodland environment.

One other rhododendron that we have that does fairly well blooming in total (bright) shade is 'Scintillation'.

Best wishes,
Mary


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RE: Rhododendron Bloom in Full Shade?

I forgot this one: Loder's White. It blooms beautifully in the shade. It blooms a small bit every fall too, but that apparently doesn't subtract anything from its large spring bloom. And it's fragrant. An early bloomer, it blooms with the early Karume azaleas (like Snow and Hinodigiri). Its bloom period overlaps slightly with the large-leaved azalea 'Treasure', which is also fragrant. Standing in the vicinity of the two when blooming together and overlapping one another is quite a treat.

Best wishes,
Mary


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RE: Rhododendron Bloom in Full Shade?

Rhododendron buds are formed in early spring except on R. camptschaticum and azaleas like the encore type. Any bud that opens or partially opens in the fall is lost to the following spring's bloom. So it is more correct to say that in your case, fall bloom doesn't noticeably affect spring bloom.


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RE: Rhododendron Bloom in Full Shade?

>Rhododendron buds are formed in early spring except on R. camptschaticum and azaleas like the encore type.

Hi Rhodyman,

That's not what I see here. Our rhododendron and azalea buds are formed from about July onwards through the fall.

Bear in mind that we use no chemical fertilizers of any kind here on our plants, so there's no chance of artificially stimulating an unnatural early bud set here.

>So it is more correct to say that in your case, fall bloom doesn't noticeably affect spring bloom.

I'm guessing not. Not according to what I see.

I have looked hard in the spring and failed to find any terminals without a bloom. That is the case even given that there have been terminals with blooms in the fall for many, many years now. Of course, I might not have seen everything; it's in a position where I can't walk up close to give it a more thorough inspection than from about ten feet away. So I'm not totally certain of this, but my belief is that after the fall bloom here in North Carolina the rhododendron is able to set more buds before the spring bloom period. This might be much more likely where winters are warmer than in Pennsylvania, as well as in a situation where a rhododendron's shade is provided by deciduous trees. Those deciduous trees stop providing shade and increased coolness every year in the fall just after the bloom period, perhaps fooling the plant just a bit into a longer fall behavior than otherwise might occur. Fall behavior for rhododendrons here includes setting buds, as opposed to what you see in the spring there.

And our Loder's White might have less of a clear signal that really cold weather is right around the corner than most rhododendrons in most situations do, especially compared to your situation in Pennsylvania. In fact, really cold weather isn't right around the corner here in most years after the leaves fall. Some years we've needed air conditioning on Thanksgiving Day. Though this past winter was unusually different in that really cold weather came about three weeks' earlier than usual. Still, our Loder's White is totally covered with blooms now, after a so-so bloom last fall of maybe six to ten terminals.

Based on what I can see, I believe those terminals that bloomed in the fall also are blooming right here now.

Best wishes,
Mary


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RE: Rhododendron Bloom in Full Shade?

Do you have any idea where to buy a R.Loderi King George ? I came across your discussion when I was searching for a place to buy one - I had seen a picture of one in a book, but have not been successful in finding a source. I was also delighted to read that CarolinaMary was growing it in North Carolina.


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RE: Rhododendron Bloom in Full Shade?

An update to my thinking about Loder's White fall blooming behavior...

>I said to Rhodyman, "Based on what I can see, I believe those terminals that bloomed in the fall also are blooming right here now."

I'm less certain of this today, and may never know for sure, without being able to get up close to the rhododendron to do a really good job of looking in both the fall and the spring. Yesterday I was looking at the plant from an angle different than I usually look at it, and from slightly higher. I saw two terminals that actually weren't blooming that I just missed in looking from below (it's halfway up the slope of a large steep berm). One terminal had several leaf buds on it and the other had a single leaf bud. Meaning that one of those terminals probably had a flower on it at an earlier point (we don't disbud--haven't done that in years) and one didn't. Whether that earlier point was last fall or earlier this spring, I can't know for sure, but I'm guessing it was last fall, as Rhodyman described.

We had 60-90 mile-an-hour winds here in the storm the night before yesterday so a spring bloom could have gotten ripped off the plant, but at least the rest of the plant looked intact (and the reason to guess that the one non-flowering terminal with several leaf buds had a bloom on it last fall). As best I can recall, the fall bloom on that plant was maybe 4-6 terminals. Anyway, Loder's White is a breathtakingly beautiful variety every spring, and it looks good in the landscape throughout the year too! And it grows well with almost no care once it has gotten off to a good start.

Whether it does or does not measurably subtract from the total number of spring flowering terminals, the fall bloom definitely does not detract to any noticeable degree in the wonderful spring bloom; it's just enough in the fall that if you can get to the plant to cut a bouquet or two to bring in the house, you have something nice to look at when most other plants are no longer producing. Loder's White is pretty much what you'd ideally like to have in a rhododendron.

Best wishes,
Mary


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RE: Rhododendron Bloom in Full Shade?

>Do you have any idea where to buy a R.Loderi King George ?

Hi Susan,

Try Greer Gardens.

http://www.greergardens.com/RHO_I-L_Rhododendrons.htm

Other potential sources might be Van Veen's Nursery in Oregon and Nuccio's nursery in California. Nuccio's will send a free catalog if you call them, and you can access Van Veen's information online.

>I was also delighted to read that CarolinaMary was growing it in North Carolina.

No, I don't grow Loderi King George. I grow Loder's White, and a progeny of Loderi King George by the name of County of York. I once thought about trying Loderi King George, since we have a relatively protected spot. But Zone 8 is what I've always seen recommended for Loderi King George and we're zone 7. On the other hand, Greer is saying it's hardy down to zero, which is what they say for Loder's White too... and our Loder's White (in a relatively protected spot) survived the winter of '81-82 with ten days not getting up to freezing and a bunch of nights down below zero to minus 6 or 8 or something like that. Survived in perfect condition!

Loderi King George is a wonderful looking plant that's quite an eye-catcher. If you can grow it where you are, I'd think it would be the absolute focal point in your yard.

Best of luck with it,
Mary

Here is a link that might be useful: Scroll down this page to find Loderi King George


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RE: Rhododendron Bloom in Full Shade?

carolinamary

I misspoke. Rhododendron and azalea buds are formed in early to mid summer, not spring. They normally bloom in the spring. So they are blooming on buds formed the previous summer. The buds that open in the fall, will not open in the next spring since they only open once, so bloom is lost for the spring. R. camptschaticum is unique in that all its buds open in the summer and none overwinter to the next spring.

On some plants like encore azaleas and R. camptschaticum, some of the buds that form in summer open in summer. But they still won't open again in the next spring. Buds only bloom once. Once they start to open, they won't make it through the winter.


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RE: Rhododendron Bloom in Full Shade?

Since the issue of 'King George' came up, anybody know of a mature plant of the Loderi grex, anywhere on the East Coast? In my discussion with someone at Rarefind, probably Hank but maybe Jerry or Ron, I was told to not even bother because they like neither heat nor cold and prefer a maritime zn 8 climate. I've seen huge ones in Seattle, unfortunately not when they were blooming!


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RE: Rhododendron Bloom in Full Shade?

I had Cunningham's White in dense shade for a few years, and had one lowly bloom, though it otherwise grew well and remained healthy. It produced buds each year, but that was it. I moved it around a couple times, trying to find the perfect location, and found that it likes more sun than I had anticipated. I'm zone 5, WI.

I also planted a Marie Fortie that was overwintered in a basement and we questioned whether it would survive, looked like it had a lot of browning of the leaves. We planted it very early spring, left for vacation to return to an abundance of blooms. I thought that they don't bloom after being transplanted, so it was a pleasant surprise. This one also receives a lot of sunlight, in a westerly location but dappled shade in the afternoon hours from a nearby tree.

This is my first year with the buds opening on my Cunningham's White, as I write this.


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