Pruning rose of sharon and dipladema

OK, I have these two shrubs (I am not sure of the spelling of dipladema as I don't have its card in front of me, but I was told butterflies and hummingbirds love them). I notice that on both, the blooms are located on new growth.
I find the structure of both wanting as both have stems that are a little less than a metre without branching. It looks like a case of strong apical dominance.
I have to keep the dipladema reasonably small because I will have to bring it in each fall (the horticulturalist I spoke to when I bought it told me to bring it in before it gets hit by frost since it is not winter hardy here, just north of Toronto - she didn't say what to do to over-winter it inside or what to expect it to do).
Both are giving a terrific display right now.
Do you have any experience pruning these shrubs? If so, when is the best time of year to prune them? And when you prune, should the focus be on thining the plant, or reducing the height? In both cases, how much should be removed? Can I thicken up the plants by snipping the shoots just below the growing tip of each stem I want to branch? If so, how much should be enough to end apical dominance in these plants and encourage the stems to branch? Am I right in expecting that doing so will improve their displays next year?
Thanks for your time.
Ted
R.E. (Ted) Byers, Ph.D., Ed.D. R & D Decision Support Solutions http://www.randddecisionsupportsolutions.com / Healthy Living Through Informed Decision Making
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Ted wrote:

I think you should go get the "card".
<snip>
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Travis in Shoreline (just North of Seattle) Washington
USDA Zone 8
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Remember, "Joker's are wild"!!!!!
Pick a card, any card!!!!!
Try Dipladenia while you're at it, Travesty.
http://images.google.com/images?q=Dipladenia&hl=en&btnG=Search+Images

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Cereus-validus....... wrote:

of the 'n', but I was close. I just checked the 'card', which was glued to the pot. I knew there was a reason I didn't have it handy.
That link you provide provided a lot of great pictures. Thank you!
Cheers,
Ted
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Rose of Sharon (Hibiscus syriacus) can be pruned back hard in late winter or early spring. Young plants typically have a habit much like you describe but will become more shrub-like with maturity. This plant is very late to leaf out so don't panic when it looks like a dead stick well into spring.
Dipladenia (aka Mandevilla splendens) is a lax, vining shrub. It too can be cut back hard as new growth begins in spring. It will need a cool, bright environment for the winter - a greenhouse is ideal but a sunroom or unused bedroom will work as well. Keep on the dry side, watering only to prevent it from fully drying out. It will need to be re-acclimated before you move it back into the garden for spring. Watch out for spider mites, which can be a problem with overwintering.
pam - gardengal

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Hi Pam,
Thank you very much. This is useful
I bought a couple winter hardy Hibiscus recently and was told, in this forum actually, that they'd likely start new growth in May. This is in southern Ontario, just north of Toronto. Can I expect similar timing from the Rose of Sharon? Does it grow rapidly once it decides to start?
For both Hibiscus species and Dipladenia species, is there any benefit to lightly trimming the stems, to encourage branching by suppressing apical dominance, perhaps in early summer and mid-summer? Or would that do more harm than good?
Out of curiousity, do you have any idea why it was called a rose when it is a hibiscus and looks nothing like a rose?
Thanks,
Ted
R.E. (Ted) Byers, Ph.D., Ed.D. R & D Decision Support Solutions http://www.randddecisionsupportsolutions.com / Healthy Living Through Informed Decision Making
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For a Ph.D., Ed.D., you ask a lot of stoopid questions, Tedious Buyer.
Why are Koalas called bears when they are not bears?
Why are "water lilies", "day lilies", "calla lilies", etc. so called when they are not true lilies?
Why is the "Rose of Sharon" named Hibiscus syriacus, when the plant is actually native to China not Syria?
Why don't you do a Google search instead of being a pest?

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Because they're naked, & they live exclusively off of kola nuts.

Since the name lily is derived from a Greek name of Narcissus, even true lilies aren't lilies.

Because missionaries in China converted it to Christianity.

Depends on what you call rapid growth. Compared to say bush mallow, rose of sharon grows rather slowly. But an well rooted long established shrub will grow back rather quickly from a hard pruning.

Prune late winter or early spring.

It's flowers look quite a bit like wild roses, but Rose of Sharon is a biblical reference not associated with roses per se, & not exclusively associated with hardy hibiscus.

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Thanks Paghat,
This was informative.I've never seen a wild rose, only the thorny treasures at the garden centre.
Thanks again,
Ted
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Thanks a bunch for 'splaining it all, Pagthagoras!!
If someone gave you a place to stand, would you leverage the whole dang earth?
If you were a Rhodes scholar, who would you asphalt?
If Dubya doesn't have a magic wand he can lower gas prices with, how in the heck did he get to be president in the first place?

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