WHEN TO PRUNE PHILADELPHUS (MOCK ORANGE) and SYRINGA (LILACS)

Philadelphus shrubs, commonly known as Mock Orange, are pruned immediately after flowering each year, just the same as syringa (lilacs).  The reason is because they flower on this year's growth and pruning them immediately after flowers have faded gives the opportunity to enjoy this year's flowers and the probability of having a good display next year.

Philadelphus 'Snowbelle' in full bloom

Now, I'm not an expert despite decades of gardening, far from it, so I do try to follow the advice of experts and specialists, as well as trying to use a bit of commonsense.  I pruned my syringas (lilacs) a few weeks ago, giving them a light prune as they are young: I have plans.  I want them to fill out and grow above the top-of-the-fence level without turning into monsters but I don't want them to be too heavy at the base and complete with smaller shrubs.  It's a matter of control and great practise for control freaks!  Leave most lilacs to their own devices and they try to reach the sky (Syringa 'Red Pixie is dwarf lilac).





Below, Philadelphus 'Snowbelle', a compact shrub that should not take up too much room in my garden border, was looking a mess now flowering has finished.  Time to prune but as it is small, I only pruned lightly, shaping it up, removing any dead and weak stems hiding in the middle of it all, and cutting back to just above a pair of leaves. 

Philadelphus 'Snowbelle' after flowering

I always think that pruning a shrub is a bit like trying to anticipate the future. You never know just how it is going to produce new shoots and whether or not your plan to keep it a certain shape will work out.  I think with gardening that we often just have to hope for the best.




Of course, you don't have to prune and a shrub will probably make at least some new growth for flowers next year without help from us, but pruning stimulates plants to put a spurt on and produce new shoots and it's also a great opportunity to stop a plant becoming an unhealthy tangled mess.  It's interesting that the harder you prune a plant, the more vigorously it should grow.  This is great for encouraging weaker stems to do better.  Plants are survivors after all.  However, the way I understand it is this: if you have a long vigorous shoot sticking out of a shrub, if you cut it hard back you will just encourage it to retaliate and show off again.




You might find this RHS Guide on Pruning Shrubs helpful (external link)

Philadelphus 'Snowbelle' after a light prune

I noticed that a sneaky blade of rye grass was growing up the middle of the shrub.  The bird feeding-station is very close by and the birds will keep dropping the rye grass seeds which cannot wait to germinate in my garden.  That's why, usually, I feed them on husked sunflower seeds.