Clippings No.1 Hydrangea pruning

With different species requiring different treatment, it's easy to get confused. But you can group them together and keep pruning nice and simple.

Welcome to the first in a new regular, weekly feature… Clippings! A short and sweet walkthrough of common seasonal gardening tasks and activities. Let get straight into it, shall we?

Identifying your hydrangeas

The vast majority of Hydrangea shrubs for sale are: Hydrangea macrophylla, Hydrangea paniculata, Hydrangea arborescens. We’ll look at Hydrangea macrophylla first because we have two subsets: The Mophead and the hardier Lacepcap.

The Mophead, or florist’s hydrangea, is the most familiar. Large ball-shaped flowerheads in pink, white, or blue. The Lacecap is the flat, umbel-shaped flowerhead with a larger set of ‘flowers’ forming a ring around the outside. They both need minimal pruning.

This is our first group.

Classic hydrangea (H. macrophylla) Photo by Simone Dalmeri on Unsplash

Next we have Hydrangea paniculata, H. arborescens. H. paniculata is the very familiar ‘Limelight’ with large conical flowerheads and H. arborescens is the increasingly popular ‘Annabelle’, with large cushion-shaped flowerheads in white or pink. These need pruning to create a strong framework for the best flowering.

This is our second group.

Hydrangea paniculata (Left) Hydrangea arborescens (Right)

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Standard Pruning

1. Prune all of these hydrangea shrubs in early spring (depending on your climate). I usually tackle mine in March, early April is fine too.

2. Always prune down to something, whether it’s a pair of buds, or a joining branch.

3. Tackle the 3Ds first. Prune out the Dead, Diseased, and Damaged stems.

4. Prune any weak growth sidehsoots.

5. Prune any crossing stems, especially those that are rubbing and creating wounds.

6. Once you’ve finished pruning, your hydrangeas will really appreciate a good mulching, watering deeply first, if it has been a dry spring.

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Pruning Mopheads & Lacecaps

Start by deadheading all the old flowerheads by cutting each stem down to the next pair of strong buds, beneath the flowerhead, working your way from the top down. If the flowerhead has fallen off already, you can still cut down to a pair of strong buds. For younger shrubs, this is usually all you need to do.

If you have mature shrubs and flowering has really slowed, you can remove a 2-3 of the oldest and woodiest stems. Cut these old stems right down at ground level and you will promote fresh new stems and more flowers (the following season).

If you have an old shrub that flowers poorly and just looks tired, you can rejuvenate the entire shrub by cutting all the stems right down at the base. Be brave! You will lose flowers for this season, but it will be an entirely new and invigorated hydrangea! I’ve taken this drastic action here and it works.

Problems:

1. Pruning too hard and accidentally removing the flowering growth for the current season.

2. Pruning too early and emerging buds are scorched by frost.

3. Mis-identifying older stems. Do this by their colour and texture. New stems tend to be dark and smooth. Older stems are straw-coloured and look more fibrous.

4. Not pruning related, but if you’ve bought a blue hydrangea and it’s turned pink, then your soil is alkaline. Blue hydrangeas need acidic soil to remain blue. White-flowering shrubs remain white irrespective of soil pH.

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Pruning Limelights & Annabelles

With these hydrangeas we’re looking to create a permanent open framework of branches, so bear this in mind…

Simply put, the harder you prune, the more vigorous the regrowth, the larger the flowerheads. So if you prune the stems to just 8-12in (22-30cm) from the ground, you will trigger strong growth for the largest flowerheads. However, they can be so large, they may need significant support.

Alternatively, take each stem down by roughly 30-40% (down to a minimum of 40cm from the ground) and you will trigger modest regrowth and many more flowerheads, albeit smaller in size. However, the advantage is that they won’t need supporting because of the stronger framework. So there’s the trade off. I know many gardeners want the biggest, showiest flowerheads, but I prefer a ‘modest’ display and no supports.

I generally prune down to within a few centimetres of the previous year’s pruning point, so I’m gradually building a strong framework. I cut just above a pair of buds, removing all thin weedy side shoots back to the stem. Any weedy stems emerging from the base are removed entirely. For those that would like to see a practical pruning demo, I’ve added this little video of me pruning some of my Hydrangea paniculata..

Problems:

1. Not pruning hard enough and having lots of leaves and lots of tiny flowers.

2. Pruning so hard, the new growth is too lush and each stem needs supporting when in flower.

3. Feeding too much also results in lush growth that needs supporting. Plants in the ground do not need feeding, just a good mulch.

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What would you like to see on Clippings?

Next up in Clippings, I’ll be potting-up Dahlia tubers, but there’s a wide range of topics to choose from: Pruning, watering, feeding, weeding, sowing seeds, planting, mulching, potting plants, composting, deadheading, garden tools, etc. Do let me know in the comments. Also, as this is a new feature, I would love your feedback.