Rhododendron pruning/reporting timing

[apolaine]

On a whim a couple of months back I grabbed this half price rhododendron at the garden centre. It had already blossomed and was looking pretty sorry for itself. I pruned back a little and cleaned up a little and it seems to be a bit more stable.

I don’t really know if this will ever make a decent bonsai. The leaves, even new ones are 3-6cm long. Nevertheless, I’d like to work on it a bit. I’m been reading around and am still completely unclear on the best time to do structural pruning on these and when to repot. Early spring as with most trees or Autumn? I can see flower buds have pushed where I pruned back, so I assume I’ll have a season without flowers.

Any tips or links?

 

[Deep Sea Diver]

Not many folks Bonsai Rhodys compared to azaleas. They are all one big family, in fact azaleas, according to some experts, are really Rhodys, but the azaleas folks didn’t want that to happen in name.

Anyways you can treat Rhodies just like you treat azaleas in most respects, it’s only a difference in scale. Pruning, flowering, potting. I’ve multiple in ground rhodies here that I treat just like the azaleas I have. Some are even potted up.

Most folks prune right after flowering, but you can prune as late as 8 weeks before expected frost. Here that means mid September. It just also means that areas you prune late may not develop flowers.

One thing you can do now is look for areas that have multiple branches coming out of the same point and reduce these to two horizontal branches and cut these back to two leaves for ramification, taking into account your ultimate design.

Here’s a photo of an in ground Rhody that was severely cut back in a high and tight pruning 7 weeks ago. You can see it’s back budding just like azaleas, in profusion.

Cheers
DSD sends

 

[apolaine]

Thanks. Yes, I’ve heard most people don’t do Rhodys and actually this was a mistaken buy (I hadn’t realised the relationship between them and azaleas and thought the words were used interchangeably here in Germany). I might just go for it - for a 9€ bargain bin plant there’s not much to lose. Though having rescued it I’ll try not to kill it.

 

[0soyoung]

There are a number of dwarf rhododendrons that are suitable for bonsai. 'Carmen' and 'Blue Barron', as examples that I've enjoyed.

 

[Leo in N E Illinois]

It is botanically correct to call any and all azaleas, Rhododendron. The bulk of the Rhododendron species however can not be called azalea. The azalea is a narrow sub-group of the Rhododendrons.
There is no significant botanical distinction between Rhododendron and Azalea, so the name azalea is botanically meaningless. However, horticulturally, leaf size and number of flowers in a truss and number of stamens in the flower more or less define azalea. Since bonsai is a sub-set of horticulture, we use the term azalea and specifically mean those Rhododendrons with relatively small leaves, with hairs on the leaves instead of indumentum, flowers that are in trusses of 4 or less, and flowers of the "true Satsuki azalea", which is another botanically meaningless term, will have only 5 stamens. Everything else in the genus Rhododendron is a "Rhodie".

Your "Rhodie" has large leaves. There is a fair body of experience, it is safe to say the leaves will never reduce in size enough to successfully create a "bonsai image". Rhodies also will require a pot with more depth than is typically used for bonsai, pots need to be deep to accommodate sufficient roots to keep the rhodie happy. "Tubs instead of bonsai pots". Since the Rhodies are evergreen, there is no point in time when they will be leafless, so you can not make a "single season bonsai" the way that is done with deciduous Magnolia, which bloom while leafless, or Wisteria, which bloom just as new growth is appearing. Wisteria grow so rampantly they are never displayed except when in bloom. Otherwise the ugly, rampant vine is hidden away in the back corner work section of the bonsai garden.

So the result is a large leaf Rhododendron will never make a successful bonsai. However, you can use bonsai techniques to train the trunks of a Rhodie, and create a very pleasant tree in a tub. It won't be considered bonsai, but it certainly become an attractive garden plant. So go for it. And certainly show us photos of it in flower each year. We have a "Flowers" photo thread on BNut, where the Rodie would be appropriate regardless of it not being bonsai.

 

[Leo in N E Illinois]

There are a number of dwarf rhododendrons that are suitable for bonsai. 'Carmen' and 'Blue Barron', as examples that I've enjoyed.

THe above is true, When I said that @apolaine 's original tree would never be bonsai, I was referring to that specific plant in the photograph. There are indeed many Rhododendrons that have small leaves that are not considered to be "Azalea" that make great bonsai. Key is, you need to find the Rhodies with small leaves. Some examples are
Rhododendron dauricum, R. fastigiatum, & R. minus. One of the hybrids, common in North American nurseries is R. Purple Gem (fastigiatum x minus), it is winter hardy to zone 5a or 4b, has small leaves and makes a "pretty good" bonsai.

 

[apolaine]

Thanks both. I think this one is destined for pruning practice. I have two large rhododendron bushes in my garden already. And old wisteria, incidentally - I’ll air layer one of them soon.

 

[0soyoung]

Rhododendrons with which I am familiar produce a flush of growth and then set flower buds in advance of the summer solstice. There are some very early season blooming azaleas that don't require vernalization and behave likewise.

A flower bud is easily recognized as being a fatter terminal bud. Don't prune those off, it you want flowers next year. A flower bud is is metamorphosed vegetative bud. Once a vegetative bud is morphed to being a flower bud, it will not change back and that stem will cease to extend - there may be growth from axillary buds behind the terminal, however.

Alternatively, if you have a rhododendron branch extending new growth now (well after the summer solstice), it doesn't have a flower bud.

 

[0soyoung]

My rhododendron 'Blue Barron' --> two new shoots coming from below the terminal flower bud.



Those shoots could be pruned or left to grow with no effect on the flower bud (though aside, note that this is what satsuki azaleas do in spring = grow, then bloom, then grow again).

Also two new shoots from below a bud that is now barfing up a flower pair.



Leaf sizes are comparable to those of most evergreen azaleas. The flowers are the whole reason



This normally blooms in early spring, but some buds got triggered to open now.

 

[Carol 83]

My rhododendron 'Blue Barron' --> two new shoots coming from below the terminal flower bud.

View attachment 327546

Those shoots could be pruned or left to grow with no effect on the flower bud (though aside, note that this is what satsuki azaleas do in spring = grow, then bloom, then grow again).

Also two new shoots from below a bud that is now barfing up a flower pair.

View attachment 327547

Leaf sizes are comparable to those of most evergreen azaleas. The flowers are the whole reason

View attachment 327548

This normally blooms in early spring, but some buds got triggered to open now.

I need to find one of those! Purple!!!

 

[Deep Sea Diver]

My rhododendron 'Blue Barron'

Leaf sizes are comparable to those of most evergreen azaleas. The flowers are the whole reason
This normally blooms in early spring, but some buds got triggered to open now.

Nice!

That’s interesting to hear as one of my Rhododendrons has taken to have a partial bloom in October for two years running.

When I went to Kobota Gardens last fall there were a few similar Rhododendrons also partially blooming.

I think they’ve taken to being Australian!

cheers
DSD sends