Is your Butterfly Bush getting unruly? These vigorous shrubs can easily become overgrown and messy-looking if you don’t regularly prune them. The good news is that trimming a Buddleia is pretty simple with a little bit of preparation and know-how. Here’s everything you need to know to properly prune your Butterfly Bush.
The best time for major pruning on a Buddleia is the end of winter or the beginning of spring. It’s often best to trim larger varieties once every one to two years to encourage blooms and keep the plant tidy. You can hard prune your Butterfly Bush if you prefer; just make sure to disinfect your tools.
There’s practically no wrong way to prune a Buddleia. It’s not uncommon for them to grow back from the rootstock, even when cut to the ground. However, the amount of trimming and shaping your plant requires may have a lot to do with your local climate. As you read the advice below, remember that we only offer general guidelines. There’s no substitute for observing your own Butterfly Bush and learning what it needs to stay healthy!
Why Prune Your Butterfly Bush?
If you’re new to growing a Buddleia, you might be wondering if the plant really needs pruning. While it may not always be necessary, most people growing them as garden or landscape plants find that pruning makes for a better-looking Butterfly Bush. Here’s what a little attention from the clippers can do for your plant:
- Increase flower production. This is the #1 reason most people trim Buddleias. Because they bloom on new wood, the number of blooms tends to drop off once they reach a mature size and their growth slows down. A yearly pruning spurs a new growth flush that will produce many flowers.
- Keep the size in check. Many types of Butterfly Bush can get quite tall and wide. Without pruning, they may sprawl out of the space you’ve allotted for them. And since the new growth forms at the top, the flowers can be high up and hard to see. Certain hybrid varieties can also be unstable if they get too top-heavy for the roots to support.
- Create a more graceful shape. An un-pruned Buddleia often takes on a shaggy appearance. Cutting it back helps to keep it more well-rounded. You can even train it into a tree-like form with a little patience.
- Prevent it from escaping. In some parts of the U.S., Butterfly Bushes can be invasive because their seeds spread so rapidly. Late summer pruning to remove the blooms before they set seed can keep them contained.
- Encourage reblooming. Another benefit of deadheading spent flowers is that it frees up energy for the plant to grow new ones. If you time it right, you may be able to extend your Butterfly Bush’s blooming period substantially. It will also simply look better without withered, dying flowers.
What’s the Best Time to Prune Your Butterfly Bush?
The ideal timing for Buddleia pruning depends on what you’re trying to do. You can trim at almost any time if the goal is just to remove a few untidy-looking branches or remove spent blooms. But if you want to do a major cutback to invigorate your plant for the season and/or control its size, you should prune your Butterfly Bush in the late winter or early spring.
If you leave your annual pruning too late, your Butterfly Bush will have to sprout its new growth all over again before it can bloom. You’ll likely wind up reducing its flowering season this year. But if you trim too early, a late frost could damage the new wood. It’s best to do a little bit of research and figure out when your area should be safe from cold snaps. A good rule of thumb is to wait until the first buds or new leaves begin peeking out.
Some gardeners like to do their yearly Buddleia trimming in the fall or winter. This can work and won’t shorten the flowering season, but it will slightly increase the risk of cold damage. The spongy centers of Butterfly Bush stems may hollow out after being cut back. If water gets into the cavity and freezes, the stalk can burst and split, potentially harming healthy tissue further down.
Pruning for Reblooming
What if your goal is to produce a second flush of blooms? In that case, you should deadhead your Buddleia in the late summertime, removing the older flowers. Try to do this just as they’re starting to show their age. The exact time will depend on your region, but mid-August is a good bet.
Keep in mind that some modern hybrid varieties of Buddleia don’t require deadheading in order to rebloom. They’ve been bred to continue popping out fresh flowers all summer long.
Summer pruning can also help you keep your plant’s size under control. If you’re trimming for this reason, you can cut back more or less as far as you want rather than just deadheading spent flowers.
It may be best to do this type of maintenance pruning a little bit earlier — think late July or early August. Large-scale pruning at the very end of the summer could mean that your Butterfly Bush heads into winter covered with tender, brand-new growth. This makes the plant more vulnerable to frost damage.
How Far Back Can You Cut Your Butterfly Bush?
There’s no set formula for how much you can remove from a Butterfly Bush. Lots of guides suggest taking them down to between 12 and 24 inches, but that’s mostly just a guideline to help you keep it at a reasonable height. It’s safe to cut a Butterfly Bush all the way back to the ground if you’re really trying to limit its size.
What if you have an older Butterfly Bush that hasn’t been pruned in years and has stretched to 14 or 15 feet tall? With a shrub this old and well-established, it may best not to prune it to the ground all at once. This could be a fairly severe shock. Instead, we’d suggest cutting it down to around four or five feet tall, waiting a year, then cutting back further if needed.
Butterfly Bushes grow fast, especially when they’ve recently been pruned. Many varieties can gain more than six feet of height in one year. You can often figure out how much to cut by simply deciding how high you want it and subtracting five or six feet. Dwarf varieties may be a bit slower, but they can usually go from a few inches tall to their maximum height in one growing season.
How to Prune a Butterfly Bush
Here’s how to give your Butterfly Bush a major pruning. (We’ll cover lighter trimming and deadheading a little further down.) Follow these steps if you want to keep your plant to a manageable size while encouraging a burst of healthy growth and blooms.
Step 1: Get Your Tools Together
The first and most critical thing you’ll need is some cutting tools. A handheld set of pruning shears should be fine for pruning thinner and more herbaceous growth. If you prune your Butterfly Bush back sharply every year, these small trimmers may be all you’ll need. For woody stalks that are more than half an inch around, you’ll probably want some bypass loppers, which are sturdier and offer better leverage.
If you’ve gone a long time without pruning your Butterfly Bush, it may have some seriously thick stems, more like tree limbs than branches. These may call for a more heavy-duty tool like a hand saw. This is the tool to reach for when you need to cut through something thicker than 2-2.5 inches.
You should also have a chemical disinfectant for your blades. Rubbing alcohol is our go-to choice, but you can also use bleach diluted to 10% strength. Grab a clean rag or two that you can use to apply your disinfectant. This will help you avoid getting fungi or bacteria in the cut.
Step 2: Remove Dead Butterfly Bush Stems
Unless you live in a very mild climate, your Butterfly Bush will most likely have some winter dieback each year. You should begin by clearing this dead growth out.
If you’re following our advice above and pruning your Buddleia in the early spring, spotting the dead areas should be fairly simple, because they won’t have any new buds leafing out. The dead stems are also usually brittle, stiff, and slightly gray. If you’re uncertain, scratch through the bark with a fingernail and see if it’s greenish and alive or brown and dead.
You probably won’t even need tools to get rid of them — you can usually just snap them off by hand. If any older, thicker growth has died back, you might need clippers or a saw to remove it.
Step 3: Examine Your Butterfly Bush From Every Angle
Before you start cutting live wood, you should get a sense of your Buddleia’s structure. Walk around it a couple of times to see how it’s growing and where any major branches are pointing. Here’s what you’re looking for:
- Overall shape. Does your Butterfly Bush have a mostly rounded growth habit? Or is it tilting to one side or sending out odd tufts of growth in certain spots? Do you like how it looks, or does it need a major reshaping? Figure out if there are any places where you’ll want to cut back more drastically.
- Crisscrossing branches. When two branches are laying across each other, the friction may scrape their bark off and allow infections to develop. You should be especially watchful for stems growing back through the center of the bush, as they’ll often overlap with several others. You’ll probably want to remove them entirely.
- Growth heading toward unwanted areas. Figure out which way the bigger branches are growing. Are any of them creeping toward walkways, windows, walls, or other spaces you’d prefer to keep clear? If so, you may want to chop them back more severely.
- Unsightly, spindly branches. You may find that your Butterfly Bush has produced a fair amount of whippy, thin growth off to the sides. This can look messy next to larger, more established stems and may spoil the look of the plant. This is mostly an aesthetic preference — feel free to leave the spindly stuff if you don’t mind it. These offshoots can grow into thicker branches in time, though removing them now may spur more growth and blooms.
Step 4: Prune the Green Wood On Your Butterfly Bush
Once you’ve identified the stems that need trimming, you can start clipping them back. Find a pair of live leaf buds at approximately the right height and snip or saw just above them. Disinfect your tools first to reduce the risk of the cut getting infected.
Clip through the stem at a slight angle, leaving only a small, slanted stub poking out past the new buds. When using bypass pruners, make sure that the flat side of the blade is touching the “lower” part while the raised edge of the hook faces the section that’s coming off your Butterfly Bush.
Now continue this process with the other stalks, disinfecting your clippers between cuts. We don’t recommend trimming everything back to a uniform height — this can look odd and artificial. A better option is to leave the tallest stems near the center and reduce the height as you move toward the edges. This should create a dome-like shape.
If you prefer a more naturalistic look, you can alternate short and long stems at random. It’s also possible to prune your Butterfly Bush into a tree-like shape by selectively removing the lower side branches.
Step 5: Watch Your Butterfly Bush Grow!
Keep trimming until you’ve cut back your entire Buddleia to your desired height. The first time you do this, it may feel strange to whittle a sprawling shrub down to just a few short stems. But your Butterfly Bush should regrow rapidly once the season gets underway. And by mid-summer, it will be sporting a splendid array of blooms.
Summer Cleanup Pruning for Your Butterfly Bush
Many gardeners find that a single annual pruning, as described above, is enough maintenance for their Butterfly Bushes. Others prefer to tidy up their shrubs once the growing season is past its peak. This can include deadheading older blooms, clipping off extraneous growth, or making a second, less dramatic size reduction.
If you’re deadheading older blooms to keep your Butterfly Bush looking fresh (and avoid the seeds spreading), you can remove them on an as-needed basis. If you notice one wilting and turning brown, grab your shears and look closer.
You may see smaller leaves pushing out of the stalk a little bit below the base of the flower spike. These can grow into new flower spikes. In fact, you’ll sometimes spot little blobs of color in the center where the blooms are beginning to form. Clip just above these emerging leaves to maximize your Buddleia’s flowering.
Some stems may not have these side sprouts. Or they may already have bloomed and started to wilt. In that case, you can prune back the entire branch to any healthy pair of leaves you like.
You can also trim off any overgrown branches that are spoiling your Butterfly Bush’s appearance. Another option is to give the plant a bit of a “haircut” all over, reducing its size a bit; this should work just fine as long as you don’t wait until too late in the season. Follow the same pruning technique we laid out above: disinfect between snips, leave a slight stub above the nodes, and cut at an angle.
Final Thoughts
When you prune your Butterfly Bush, it’s hard to mess up too badly. You can chop it back down to tiny stubs and still watch it flourish and blossom. The timing is the most important thing to get right, but there’s still a fair amount of wiggle room there. As long as you cut sometime in the spring, the worst that can happen is that your Buddleia’s flowering will be delayed.
As you get comfortable trimming your Butterfly Bush, you’ll find that regular pruning helps keep it vigorous and beautiful. It will grow faster, produce bigger booms in greater numbers, and have a more pleasing shape. Don’t be shy — cut your Buddleia early and often.