Hydrangea: why we don't prune them in March!

It is best, in the UK, not to prune bush Hydrangeas until winter is well and truly over: the books all say "prune in late winter/early spring" , which would usually mean Feb/March: but the books also say "not until the last frosts have finished," which can be as late as May.

For many years I worked for a lady with a large amount of Hydrangeas (part of her garden was actually called the "Hydrangea Walk"!) , and she would never let me cut them back until the end of May.

Personally, I prefer to prune them a little earlier than that: rather than following the calender, I assess how much they've grown, how advanced the buds are, how much dead material there is, how healthy the particular plant is, and of course the weather: what sort of weather we've had, and what sort of weather is forecast.

The problem is that if you leave it too long, until they have started to sprout, then it's tricky to cut out the dead stems without damaging the tender new leaves. But if you cut them too early, they might be damaged again, by a late frost....

Generally speaking, then, I don't have a set date: but I would never prune them as early as March.

Rather, I tend to put off pruning them until towards the end of April.  Having said that, sometimes the owner wants them cut back earlier because they are sick and tired of looking at the dead brown flowers from last year, in which case I would compromise: I would shorten the stems with dead brown buds, but I would leave at least one set of dead ones, rather than cutting right back to the live ones.

Garden owners often ask what I do with my own Hydrangeas:  personally, I nip off those dead brown flowers just as soon as they start looking tatty, which can be in autumn: I don't subscribe to this notion that leaving the dead flowers in place protects the buds lower down.

However, I most certainly do subscribe to the notion that frost damage occurs from the tips inwards: and that means that I may nip off the dead flowers, but I leave the stems long. Although I will often just "neaten up" the outline, if some of the branches are notably longer than others... I like things to be neat.

Here's an example - left - of how I like to prune Hydrangeas in late autumn. This is a large Hydrangea (not mine, this is one of "my" gardens but not my own garden), and this is what I do to it every year in autumn. 

This photo was taken in mid December: I stopped part-way through to take this photo, to illustrate how  much material I am removing. You can see that I'm cutting off the dead brown flowers, and a few inches of the stem as well - but I am leaving the stems very long, over the majority of the bush.

I have cut the lowest branches back a lot further, because in this particular case, it's a large, fast-growing bush, and the lower branches invade the path, the drive, and the lawn: and it is the top-most branches which tend to take the brunt of any frost damage.

So that's my regime: cut off dead flowers as and when they start to look tatty, by all means neaten up the outline, but don't cut the whole bush back until well into April.

Here's an illustration of what happens when the frost hits:

Here you can see a stem of Hydrangea, the root is to the left, the tip is to the right: and those black things are dead, frost-bitten buds.

This was taken in the first week of April, and we have had some hard frosts in the past week or so.

All the buds to the right, ie towards the tip, were similarly ruined.

And here - left - I am moving along the stem to the left, inwards towards the centre of the plant: and you can now see that there are dead brown/black buds in the middle of my hand, but further to the left, there are some nice green buds.

These are the ones which will sprout properly: but I won't cut the stems back yet, because we may well have yet more cold weather, and if I were to cut off all the dead brown areas now, it would expose those nice green ones to the next frost which comes along.

So, as the weather is still cold overnight, this particular Hydrangea did not get any pruning at all.

I will return to it in a couple of weeks, and re-assess it.

So that, in a nutshell, is why we don't prune them in March, but we wait... just a wee bit longer!

 

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