How to Prune Hydrangeas

Hydrangeas are a fabulous shrub for the garden. Plant breeders have done some great work over the last decade or so to improve some of the tried and true varieties (e.g. Hydrangea arborescens ‘Abetwo’ Incrediball™ is a much improved form of Hydrangea arborescens ‘Annabelle’, with the same large flowers, but on sturdy stems that don’t drop and therefore don’t need staking) and come out with plants of different sizes (e.g. Hydrangea paniculata ‘Limelight’ is a gorgeous but large shrub with green-tinged blooms. A few years later, Hydrangea Hydrangea paniculata ‘Little Lime’ came out, sporting the same colour and style of blooms, but in a more compact plant.)

Hydrangea paniculata ‘Limelight’

 

Hydrangeas are heavy feeders (i.e. fertilize them like you do your roses) but will tolerate quite a bit of shade.

Hydrangeas seem quite happy in this very shaded Buffalo garden.

 

I have two Annabelles growing along the front of our house and they’ve done wonderfully there.

 

Hydrangeas are very cold tolerant–I believe they’re hardy to USDA zone 3. They’re also a plant that keeps on giving; they start to bloom in July, hold their blooms until fall, and then, once frost hits, the dried flowers stay on the plant, creating winter interest. I often cut some and put them into my winter planter arrangements.

 

The leaves of hydrangea are quite large and leathery and are generally disease and pest resistant.

The only real maintenance they need, besides ensuring they have rich soil, is to be pruned annually. And this is where you need to know which kind of hydrangea you have, as some can be pruned in spring, as they bloom on “new wood” (i.e. parts of the plant that grow the same year the bloom forms). However, there are some hydrangeas that bloom on “old wood”, which means that you have to wait until after they bloom to prune them. All of my hydrangeas (Annabelle, Incrediball, Limelight) bloom on new wood and therefore I prune them in the spring. I did have a hydrangea (a beautiful deep pink one) that bloomed on old wood–except I didn’t realize that and I actually did it in by pruning it at the wrong time, twice. It didn’t come back for spring #3, and that’s when I read up on it and realized what I’d done. Oops.

So, follow along with these instructions only if you have a hydrangea that blooms on new wood!

This is what my hydrangea looks like in the spring:

 

You can see there are lots of stems coming out from the centre of the plant, and it’s just starting to leaf out. What to cut and where? Generally, the goal is to get a domed shape (i.e. following how the plant radiates out from the ground) making cuts about 12 to 18″ from the base of the plant.

 

 

Each cut should be made just about a point of growth (i.e. where the plant is budding):

 

Make pruning cuts just above a set of buds (where the blue line is).

 

The thing with hydrangeas is that they are big shrubs and there are a lot of stems. If you spend a  lot of time analyzing every cut you’ll never finish–just dive in and start pruning, keeping that radiating shape in mind. It’s better to keep the stems a bit longer at first, and then go in and cut further later, if you find they’re still too long (you can’t glue them back on!) I end up cutting back 1/2 to 2/3 of the plant:

 

 

 

In a couple weeks the plant will have leafed out fully:

Note: this isn’t the same plant I just pruned–this is a Hydrangea Limelight–but it shows you what a hydrangea looks like once it’s leafed out, in late spring.

 

And by mid to late summer it will be producing gorgeous big blooms again:

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