I often get questions about pruning magnolias – how, when, why, that sort of thing.
The short answer as to when to prune is never if you can get away with it.
The problem is, with many varieties, with the possible exception of Magnolia stellata and stellata hybrids, that compact shrub you brought home in the boot of your car a few years ago often turns into a massive, spreading tree in no time at all and you are faced with two options – to take it out completely or give it some serious surgery.
Pruning the ends of the branches back to make the poor thing the size you would like it to be is not an option, as unless you do this immediately after flowering, you remove all next year’s potential flower buds, and even if you do this at the right time, the tree will rapidly produce lots of strong replacement shoots, so you are back to square one in no time at all.
Ideally, if you’re thinking of planting a magnolia, you need to do your homework first and choose one of many small varieties suitable for modern gardens – those with a girl’s name like ‘Jane’, Ann’ or ‘Judy’ are a good bet. However, if you really can’t live without one of the larger types, like M soulangeana – the one most often chosen and, consequently, the one most likely to cause problems – you need to start formative pruning at an early stage, removing low and spreading outer branches if these are likely to become a nuisance. Unfortunately, it is frequently only when the tree is killing the lawn, blocking light to the house windows or occupying altogether too large a place, that you realise drastic action needs to be taken.
At this stage, if possible, your best course of action is, first, to raise the crown by removing completely, right back to the main trunk or trunks, all lower branches that make access to the ground beneath difficult, then cut out, again completely, any wide-spreading branches that are blocking light or spoiling plants growing underneath.
This, hopefully, will give a narrower tree with a clear trunk, and your problems may be solved. If not, the only answer is to bite the bullet and remove it.
The magnolia in the picture, which I was asked to sort out this week, is only a youngster, so it was an easy matter to remove the shoots that got in the way of the mower and take back side branches that would spread too far for the restricted area in which it was growing.
This will hopefully set it off on the course the owner wishes it to follow; as it grows, further pruning of the same sort will be necessary to ensure it remains within bounds while flowering happily every spring.
Ideally, the work should have been done immediately after flowering this spring, but luckily there were only a few flower buds on the pieces I cut off so we sacrificed very little for the sake of keeping it in check.