GUEST COLUMN: Rose Pruning Time

By Jason Chen, SDHS Board Member.

‘Charles de Mills’ Gallica Rose.
"Remember not all roses are the same and they should not be treated as such." - Jason Chen

Part 1 - first posted on January 15, 2021, on the San Diego Gardener Facebook Group where Jason is an Administrator.

Since we haven’t had much of a winter and it looks like there’s to be rain, it's time to start rose pruning.


"Climbers will never climb if you keep chopping them back."

· For climbers, if you have space, the goal is to fan the canes, radiating out. (photo Caption Here, there are some overlapping of branches because I am training the younger green shoots to ultimately replace the older grey ones which will be taken out later in the season.) I also peg some of the branches to the ground to get better coverage on the lower half of the wall, once the plants start growing again. When training a climber, horizontal branches are your friends. Plant growth hormones typically go to the topmost buds, but when a branch is laid horizontally, the hormones are more evenly distributed to all the buds on the branch, resulting in more growth and flowering along the whole branch.


· Old garden roses and once bloomers won’t bloom for you if you cut them back hard in the winter.


· Shrub roses often look most natural when you don’t cut more off than 1/3-1/2.


· The harder you cut a hybrid tea back the larger the flowers the plant will throw out, but at the cost of how early the first flush, frequency of rebloom and number of flowers.


· When you’re not sure about making cuts, don’t take off more than 1/5-1/4 at a time. Take a step back, walk around the bush and look ... Then go back to cut more if needed.


Part 2 - first posted on January 20, 2021, on the San Diego Gardener Facebook Group.

· If you’re going for a shrubby more natural look or, if you have them planted in a mixed border, there is no need to chop them down to nubs. Pruning harshly originated to get exhibition quality and sized flowers out of the plant. Unfortunately this comes at the expense of the overall aesthetics of the bush. I’m not a fan of the rigid and straight up “Rose garden” look. If you planted for a cutting garden then by all means do what you need to do to get the best flowers.


· Follow the general rule of opening up the middle to form an open basket. But you should know that I follow the rule loosely. I’ve seen people not do anything but take hedge clippers to them, which works but since they go nude in the winter, I couldn’t live with myself looking at mangled shrubs...


Note: I also stagger my cuts to get flowering at different heights which I’ve found also helps with air circulation. If you like the even domed look, by all means flat top it. What works for one person doesn’t always work for another.


· If you don’t trust yourself enough to make big cuts, don’t take more than 1/4 at a time, step back, look and then go back for more. Remember that the new growth (depending on variety) generally will be about a foot above each cut branch.


· Many shrub roses don’t need but occasional clipping throughout the season and if you leave the flowers in the fall to fruit, many develop beautiful and nutritious hips.


· As to questions about young/newly planted shrubs: clean them up lightly by removing crossing and the weakest growth, but it’s usually best to let it grow untouched for a year or two. Deadhead the spent blooms as needed, clipping down to the next lowest outward facing leaf of five leaflets.


As with deciduous fruit trees, clean up leaves and then spray with copper first and the horticultural oil (I usually wait at least a day or two in between). Remember to spray the ground around the shrubs as well!


· And don’t fertilize yet . . .


Part 3 - submitted by email to Let's Talk Plants! for this column.

Special exceptions for certain classes of roses.


A little back history - while most of us are used to the standard hybrid tea, floribunda, grandiflora and such, I have noticed when doing rose maintenance that people often have other classes of roses tucked in. More frequently they’re the older/antique roses and they ask, “why don’t they bloom much?”, “am I doing something wrong? There are only a few flowers in the spring and then nothing the rest of the year”.


Many people will be surprised to hear but before the 1700’s most roses found in Europe only bloomed once, at mid-summer. A glorious show but fleeting at best. As travels to the far East brought back riches, they also brought back plants; tea (Camellia sinensis) and roses just to name a few. The roses that were brought back were notable because they would be in near constant bloom, at least three seasons. The main drawback is that they weren’t very hardy. Once hybridizers got their hands on these China roses and crossed them with the once bloomers, that’s when rose cultivation got elevated and would ultimately end up with what we are all familiar with today.


Pruning exceptions:

· The once bloomers - In general once bloomers can be antiques or just older modern hybrids. If you suspect that you have one, it might help to wait a year before cutting hard into it, watch what it does, note when it flowers dead head it and see if it repeats in the summer and fall. If it is summer flowering only, then winter pruning will mostly consist of opening up and getting rid of old and crossing branches, take a little off the top and sides but never take more than 1/5 - 1/4. Just like any hedging shrub, just a shape up. The main pruning comes after the flowers (you can take out up to a half, old branches, weak growth and bringing down the height). It’s a bit harder to see where to cut when the plant is all leafed out, but the plant will flush back out quickly. Fertilize and water well after that summer cut.

‘Gregoire Staechelin’ hybrid tea/climber.

· Rambling roses - these are giants of climbing roses, hardly tame-able and not for the faint of heart or people with small spaces. A large percentage are also once blooming. Pruning these essentially consisted of keeping them inbounds, take out as much dead wood as possible(easier if it’s on an arbor where you go from underneath and clip the bottom most layer, tedious is the only word I can use to describe it). Every couple of years or if/when you need to repaint/stain the structure, they can be chopped back to a couple of strongest canes and let to resprout with a vengeance. The key thing like with many plants/trees is to train them when young so when they get mature, it’s easier to keep it in bounds. Select for a few key shoots and guide them to where you want them to go.... often times they end up taking over and make us feel like they’re in charge.

‘Paul’s Himalayan Musk’
Retraining a rambler after too much neglect.

· Reblooming China, Tea roses, noisettes, polyantha, musk roses, and others -While these are the reblooming forebears of our modern Hybrids (hybrid tea) they definitely should not be cut back as such. They naturally have thinner gangly growth that bloom towards the end. They tend to form a network of branches on which to bloom from. Treating them like a Hybrid tea often results in awkward growth and limited flowering. Cut to keep within bounds but don’t cut out all skinny, thin growth, they need those to build up a good framework. In essence, they’re shrub roses that need minimal care.

Above: ‘Madame Berkeley’ tea rose with shrubby growth. Summer and fall flowers


· carpet/groundcover roses. Like climbers a good framework is important but don’t cut the canes too short, too often or you’ll never get the coverage you’re looking for. Just like if you want your hair to grow longer, you wouldn’t constantly cut it short...


· Hybrid teas, grandifloras and the like -


A tip: the harder you cut back, the longer it will take the flush out new growth. The less you cut, the earlier it’ll bloom for you. You can always cut out 1/3 to 1/2, open up the crown, take out old and diseased wood and still get a good flush of blooms. Cutting less also results in a more balanced/natural looking shrub with a more continuous cycle of blooming.


· Height - Keep in mind, if you ultimately want the blooms at a certain height, say at about 4ft. You’ll generally want to prune to about 1-1.5ft below that point, the pruned shrubs will be about 2.3-3ft.


· Wait until the end of February-March to fertilize.

· If you had issues with powdery mildew, rust and sawflies. Make sure you clean up all leaves, spray the plants and soil surface with both copper fungicides (or your fungicide of choice) and dormant oil spray. I generally do it 2-3 times (probably overkill . . .) first copper, wait a day or two and then dormant oil. Some people do both at the same time but in my mind, oil and water doesn’t work well and I want a solid coverage of each.... also Certain fungicides do not play well with Horticultural oil! Do your homework before mixing!

Board member Jason Chen is on Facebook (either Jason Chen, or JC Botanical Designs), and Instagram (grevillea01), friend him at your own risk.

  

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