When it comes to pruning magnolias, my first piece of advice would be to ask yourself this question: Do I really NEED to?
Not “Do I want to?”
Or “Should I?”
But NEED.
If there’s one thing you should know about magnolias is that they don’t respond well to aggressive pruning. And this applies both to the evergreen magnolias and the deciduous ones.
So why am I writing an article on how to prune magnolias?
Because for me, this year the answer to the “Do I really NEED to?” question is YES! And I’m counting on the fact that the benefits of pruning my magnolia shrub will outweigh the possible downsides.
Here’s why I decided to prune my magnolia when all the experts say you should think twice and (maybe) prune once.
We’ve had some very wet years in my gardening zone, with rainy springs all the way into late May. So over the past two summers, my magnolia has been covered in fungal leaf spot (most likely Phyllosticta sp.). The spread starts gradually at the end of May and beginning of June, then takes hold of the entire shrub for the rest of the summer until the leaves start falling in late October.
Fungal leaf spot will not kill the magnolia, but it won’t make it look pretty either. In theory, I get around six weeks of lush and fungus-free foliage. In practice, I have a sick-looking shrub in my garden for most of the growing season.
The other problem is that this magnolia shrub is tucked between a camellia and a Spirea japonica. Even though all these shrubs are located on the sunny side of the garden, the larger they all grow, the more tough choices I’ll have to make.
I didn’t choose this shrub sandwich. I inherited the layout from the previous owners of our house. And I suspect they planted the shrubs as young plants a perfectly fine distance apart, but didn’t anticipate how large they would grow. (Incidentally, that is mistake number six on my list of ten perennial planting mistakes to avoid in spring.)
So I’ve decided to work with what I’ve got and make the best of this setup by thinning out the magnolia a bit to allow the air to circulate more and hopefully prevent some of the fungal spread.
When is the best time to prune my magnolia?
Like most shrubs that flower early in the year, magnolia blooms on old wood. This means the cotton-candy-like blooms that I got to enjoy in March and April were already set on the branches late last summer and early fall.
So the best time to prune my magnolia is once these flowers are spent. In my garden, this translates to around mid-May.
This timing allows me to enjoy this year’s bloom as long as possible (including harvesting the flower petals for consumption) and thin out the branches way ahead of time before next year’s buds start to set in late summer.
3 Things I’m thinning out when I prune my magnolia.
1. I remove the basal shoots.
The basal shoots (also known as suckers) are the weak stems that originate from the crown of the shrub, all the way down at the soil level. They’re the first to go because they unnecessarily crowd the plant from within.
This magnolia shrub is at least seven – but most likely ten – years old. This means that it has already developed strong leaders (the older branches that give shape and structure to the shrub). This, in turn, means that there’s no need for the basal shoots to be trained into new leaders.
In other shrubs, such as some roses, the older leaders become unproductive and we need to remove them every few years and train new leaders. But it doesn’t work this way with magnolias. The old leaders will continue to bloom just as profusely, so I’ll just leave them in place and work around their shape.
So let’s prune these suckers as low to the ground as possible.
2. I cut off the dead wood.
Even for this shrub that’s always within my line of sight in the garden, it took a much closer inspection to discover that it had a couple of dead branches in the back, rubbing against the fence.
They were completely dry so I didn’t even have to prune them. They just snapped off in my hand as I was trying to inspect them. I went back and made a clean cut of the stubs left behind.
3. I prune offshoots that rub against other leaders.
Here comes the tricky part. I’m starting to cut into perfectly healthy and lush foliage, so it feels very counterintuitive.
But then again, I have to keep my pruning goal front and center in my mind: to thin out the growth in order to improve airflow and give the magnolia a chance in its fight against fungal infections. It’s worth missing out on a few branches, I think.
First, I start by noticing what branches rub against each other the most. Some only do when strong winds sway the entire frame, and those are the ones that I leave alone. Others visibly rub against each other one hundred percent of the time, so one of them must go. In some cases, we may need to prune off more than one.
Generally, I start by removing some secondary branches (the ones that shoot off the leader) and tertiary branches (offshoots from the secondary branches). This lightens the canopy to allow more sunlight in. In turn, this will help dry off the dampness after a string of rainy days.
I don’t remove all of the secondary and tertiary branches, just the ones that rub against a main branch or another secondary one.
And I always follow the one rule of thumb for pruning magnolias: even when you have a pruning goal in mind, don’t remove more than a quarter of growth. It will take too long for the magnolia to bounce back, if it ever does.
Just by removing these three elements, I can already see ‘through’ the shrub a bit better.
Do you have five minutes to repurpose the pruned material?
If you already feel bad that you’ve hacked away at perfectly good branches, I have an idea that will make you feel better. (At least, it helped me feel better).
You can treat (some of) the prunings as starter cuttings for new plants.
You won’t be able to use all the pruned material, of course. So look for semi-hardwood that doesn’t have a bud. The straighter your cuttings are, the more you can fit in your propagation container.
I was able to collect a handful of cuttings from the plant material I’ve thinned off my magnolia.
I’ve cut every section just below a leaf node, then scored the bark on the bottom of the cutting a bit to expose the layer underneath.
Then it’s just a matter of sticking it in the ground – with at least one, but preferably more nodes buried below soil level. The tricky part is keeping it out of direct sun, and keeping the container moist enough but not too soggy.
If you’d like to follow a more in-depth tutorial on how to propagate cuttings, have a look at the steps I describe in this article on taking rhododendron cuttings.