Rhododendrons: Pruning or cutting back rhododendrons

A friend asked me today what is the best time to prune or cut back her rhododendrons that are quite tall - eight to ten feet - and are blocking the view. I have heard about the 1/3-1/3-1/3 rule, but in fact I have known of several cases where rhodos have been cut back to stick size, with no leaves on, and they have recovered very well. Is now a good time to prune, as we enter Spring? Or would it be better to wait until after flowering, or even into late fall? Here on the West Coast of British Columbia, the climate is quite mild, and this winter has been exceptionally mils (so far!!!)

Looking for expert advice, Louis Peterson.

 

I would suggest pruning after flowering. that gives them the maximum time to regenerate growth in season. Look for dormant aka latent buds, they will show you where a Rhodo will be likely to regenerate.

 

I agree with Paul, the best timing for a severe pruning is just as flowering finishes. I have cut rhodies almost to leafless stumps at that time, cutting above a plump dormant bud on each limb. They grew nicely, and with a little new growth pinching ended up as compact, full plants in 2-3 years. (You do sacrifice blooming for at least 1 if not 2 years).

 

Although it is no doubt better to prune right after flowering, I cut back a rhodo last year in mid-June, and it had sprouted new growth by the end of July. The new growth still looks pretty good now, so made it through winter (well, what we had of it) just fine. I couldn't for the life of me see any dormant buds before pruning, so I just cut at random back as far as I needed the branches to go - into three-year-old wood at least. All branches sprouted quite near the ends.

 

Ability to respond varies with kind of rhododendron. Some do not break readily from old wood. Others come roaring back even from stumps.

 

Yes, the ponticum here, which is tough, spreads like a weed and cant get enough of being cut down to the ground with a chainsaw ;o

 

Thats sound advice from Ron, excercise caution as some rhodos will never recover from a severe pruning.
Regular maintenance of Rhododendrons is preferable to a hard pruning, after they finish flowering, remove the spent blooms, you dont want seeds as this just wastes energy, you can cut back a little into the older wood, 2 or 3 inches, this encourages multiple buds to break, giving a much bushier plant.......if you leave the seed heads on, usually only 1 shoot will grow, making a leggy plant.

 

Ron and anyone else who's found a rhodo who responds to pruning, Do you have the variety names? I'd really appreciate the reference to these as I am asked these questions from a design point of view and I don't have enough current knowledge.
Always looking to learn.

 

I would add that the prune severly just after flowering rule really does mean just after. If you get delayed, the plant will expend it's energy into the newly developing leaves which will make it a "hungry" time for the plant, and less beneficial in timing. I have also seen rather remarkable results from cutting Rhodos back to stumps in mid- July to early August. Cut back late in the season, the plant then uses its energy to form buds, the buds overwinter fine (even here on the coast of Maine, zone 5) and the buds are ready to sprout handsomely in the spring. Several advantages: bloom season spared, stumps are quickly sprouting rather than slowly reforming buds in late spring, and you are probably less busy in early August too. Of course these discoveries were initially accidents, as a ruthless bonsai guy meant to eliminate the rhodies in question, and we just watched them regenerate beautifully thereafter. So crisis really is opportunity in this case. I would love to add our success stories to a list of "Those that regrow" if this gets started.

 

Your friend may want to consider moving the large rhododendrons that are blocking her view. It seems a shame to continually fight with a rhodo that naturally wants to be quite large. You don't mention how old these plants are but I expect a pruning now will just have to be repeated in a few years. Moving them to a site that is more suitable - even if they have to be pruned to move them - and replacing with varieties that stay a more manageable size might be an option to consider.

 

Anne, the one I cut back was a Loderi King George.

 

Hey Karin,
Thank you! Loderi King George.... OK I have a friend who, like me, is an old wife and we swap tales. She says if the stem/stalk of the Rhodo is 'pimpled' in tiny green dots, they are the candidates for the harder pruning, otherwise go for the usual logical pruning rules. I have a tendancy to grow these and pieris utterly great or I kill 'em ugly. It's a learning process I tell you, as a few of mine are superb, so I realise I know something! I've just been familiarized with the terms elepidote and lepidote, indumentum and a few others. Oddly enough, they were terms I knew only through reading but understood concepts through working with them in the real world.
so much more to learn!
Thanks Karin

 

And now we will all be looking for tiny green dots... and I see I will have to read my Rhodo book instead of just looking at the pictures :-)