How to Prune Deadwood from Hydrangea macrophylla, Bigleaf Hydrangea
Hello there! Are you researching for garden clean-up this spring?
Is pruning Hydrangea macrophylla (bigleaf or French hydrangea) a bit of a mystery to you?
Have you been admonished one-too-many times not to prune off this year's flower buds?
We've been there.
It will take you only a few more minutes of study to "get it." We got it! (The hard way too - meaning we've pruned off this year's flowers and lived to tell the tale.)
Why Are You Researching to Prune a Hydrangea?
There are three reasons to prune Hydrangea macrophylla and Hydrangea serrata:
- To deadhead spent flowers. An essay from earlier this month explains how to deadhead your macrophyllas.
- To reduce the size of the shrub. Some hydrangeas grow HUGE and have outsized their area. Smart pruning after flowering dials them back so they fit in again. (Article coming this summer 2018.)
- To prune out deadwood. This is why we've gathered here today. Read on!
Deadwood in a hydrangea is defined as last's years stems/branches that have died. They look coarse and scraggly and it's time for them to go.
Removing them improves aesthetics and opens up the plant to airflow (important to help reduce diseases in the Deep South), plus removing deadwood creates space for new growth.
You'll also see deadwood called "winter kill," explained a little further below.
Pruning Deadwood from Hydrangea macrophylla (Hydrangea serrata too)
Earlier this month we helped with garden clean-up in Mike's mom's garden and filmed this short video to show you how to prune out deadwood. (Essay continued below the video. Please don't stop here!)
Prune out Deadwood in Two Ways:
- Prune off dead stem tips. Sometimes just a few inches of the stem tips are dead. Prune them off to the first pair of live buds. This pair of live buds is called a node in botany - a node is the point where leaves were attached to a stem and it's also the point where new buds/growth develops on a stem.
- Prune off dead portions to the point of attachment to live wood. Follow the dead growth all the way down to where it meets the live branch it's growing out of, then prune it flush with that live stem. This is shown in the video.
- Prune out entire dead branches from the base or center of the plant. Reach in and snip as close to the base of the plant or to the ground as you can get. It's pretty crowded down there, so you might not always be able to get in there deep. Sometimes these brittle dead stems even snap off in my hands as I reach down to snip them. That makes it a little easier because I can stop reaching. It can be relied upon that if they are that brittle, then they are 100% dead and have been for a while.
Removing deadwood is low stress and easy, unless you accidentally prune the wrong branch, a live branch (yes, we have become disoriented and snipped off the wrong branch many a time!). Like I said earlier, we lived to tell the tale.
When pruning out deadwood, you're not pruning off this year's flower buds/flowers because the goal is to avoid live wood. Snipping out deadwood will preserve all of a mac's or seratta's flowers for this year because you're not removing any live wood with the potential to flower. Phew. You're safe!
When to Prune out the Deadwood
Removing deadwood is necessary only once a year - as winter draws to a close. Hydrangea macs and serratas stay in good shape most of the year, but winter, even the mildest of winters, seems to kill at least a few stems. Harsh winters will kill out all the stems and you'll need to remove all that deadwood, being careful of the new growth sprouting from the base of the plant. This is why a hydrangea with dead stems is referred to as having gone through winter kill or why somebody may say "winter kill was bad on the hydrangeas this year."
Because of winter kill, we remove deadwood in late winter/early spring as new growth is beginning to expand from those buds at those nodes we told you about.
At that time, it's clear beyond doubt which branches are alive and which are dead because the dead branches aren't pushing out any new growth. They look dead while the one next to it may have exciting green growth up and down the stem. It's alive!
It's pretty obvious which is live wood and which is deadwood. Snip and the deadwood's gone without too much worry.
What to Look For
We say it's completely obvious what to look for, but that's a smug statement because we've pruned a lot of old dead wood and have really bonded with the process.
Many years ago, I was intimidated by bigleaf hydrangeas so I spent a lot of time studying the stems (this was in the dark era before it was possible to study topics on YouTube).
Before you start, spend a few moments studying the stems. Here are a few pointers to look for and observe about dead wood in hydrangea macs and serratas:
- Stem color will be slightly different in deadwood. Live wood is a darker tan, while deadwood is a lighter tan.
- The turgidity of the stem. If it's alive, it's turgid with water. Another way to say that is it's swollen with water. With life. If the stem is dead, it's starting to shrivel because there's no water, no life.
- No live buds. Live buds are plump and a vivacious green or brown. On deadwood, the buds are a lifeless brown because they are starting to shrivel like the stem or the buds may have completely shriveled and fallen off.
- No new growth. If the stem is alive, it's flushing with green leaves in March in the Deep South. That vivid life will be in stark contrast to the deadwood. However, it may be in various degrees of flushing, based on microclimate, i.e., close to the house may be flushing before the other side of the plant. This is why we went through the other observable steps before this very obvious one. When in doubt, start at the beginning with color, turgidity, and live buds.
- When cut, the pith is tan rather than green. A live stem has alive-looking pith. When dead, it's light brown and even the pith is starting to shrivel. You probably already thought to yourself that if it's alive and you cut it and see live pith, you might be heartsick. Yes. We don't want this to happen. Here's my technique and why this observable feature is important, sometimes when I'm still doubting if it's alive or not, I snip off the stem down to the closest node. If the pith is alive, I stop right there. If it's dead, I go to the second node down the stem. If it's dead, I keep working my way down from there until/if I reach a life portion of the stem. Moral: sometimes stems don't die all the way down and you can salvage some buds by working your way down the stem like this.
Pruning Deadwood from Other Types of Hydrangeas
All common hydrangea shrubs need deadwood pruned out, including Hydrangea macrophylla, Hydrangea serrata, Hydrangea paniculata, Hydrangea quercifolia, and Hydrangea aspera.
However, deadwood is more prevalent in Hydrangea macrophylla and Hydrangea serrata than in the other species.
That pretty much covers the ins and outs of pruning deadwood from hydrangeas. Is there anything we didn't cover about pruning deadwood that you're still curious about?
Did we miss anything? Please let us know in the comments section below.
Hillary & Mike