When your Butterfly Bush is healthy, it can be one of the most prolific late-season bloomers in your garden. As such, it can be a serious disappointment when this plant’s flowering is subpar. If your Buddleia isn’t producing the kind of display you were hoping for, it’s usually due to one of a handful of common problems. We’ll review the most prominent Butterfly Bush bloom issues to help you figure out what went wrong.
Late or sparse flowering from a Buddleia is often due to a lack of sunlight — these plants need full sun to thrive. Other common Butterfly Bush bloom issues include poor drainage, improper pruning, or an excess of nitrogen-based fertilizer. Pest damage can also hamper or stunt flower formation.
Most of these issues are fixable, though some are easier to correct than others. If you know what you’re doing, you may be able to get your Butterfly Bush blooming again, or at least ensure that it can produce a healthy crop of flowers next season. Read on to learn how to diagnose and treat the most likely problems with your Buddleia’s blooms.
Problem #1: Not Enough Sunlight To Bloom
The simplest explanation for a Buddleia’s failure to flower as expected is that it doesn’t have enough energy. When a plant is lacking in resources, the first things it tends to cut back on are expensive extravagances like flowers. After all, while blooms are essential for reproduction, they contribute basically nothing to the plant’s survival.
Butterfly Bushes need quite a bit of sun to fuel their rapid growth habit. If your plant isn’t receiving at least six hours of direct sun per day (on average), it’s probably feeling underfed. Ideally, you’d want to ensure it gets eight hours or more.
When poor blooming is due to a lack of sunlight, it will often be accompanied by leggy growth. The stems may seem long but bare, with so much space between the leaves that it looks like your plant is balding. You can also pay attention to the shifting patterns of light and shade throughout the day to see whether your Buddleia is spending enough time in the sun.
What if it’s not? In that case, your course of action will probably depend on the overall layout of your garden. If your Butterfly Bush is getting overshadowed by other plants, you might be able to prune the offending branches.
But maybe you like those plants the way they are, and you don’t think you could trim them enough without harming their health or appearance. Another option is to transplant your Butterfly Bush to a better-lit location. It’s usually best to wait until the following spring to make this switch.
Problem #2: Pruning Your Butterfly Bush Too Late
Pruning at the wrong time is another common source of Butterfly Bush bloom issues. The flower buds form on fresh growth, sprouting in late spring and blossoming at the height of summer. This is often referred to as blooming on “new wood”.
If you trim your Buddleia after it’s already produced lots of new shoots, you could be removing this season’s flowers without realizing it. You may still get some blooms from secondary buds branching off to the sides of the stems. However, they’re likely to be smaller than normal, and they’ll probably appear much later in the growing season. If you’re seeing a serious delay in flowering, this could be the reason why.
There’s not much to be done about this issue except wait. Enjoy any blooms you do get, and next year, save the large-scale pruning for the beginning of spring. When giving your Butterfly Bush a serious haircut, try to time it for just before or just after its leaf buds begin showing signs of life.
Problem #3: Pruning Your Butterfly Bush Too Little
Though chopping back your Buddleia at the wrong time can limit flowering, so can forgetting to prune it. Since a Butterfly Bush flowers on new shoots, any reduction in growth will tend to reduce blooming as well. When the plant hits its mature size, and its annual growth begins to taper off, it may start to flower less and less.
This problem can be compounded by the fact that many varieties of Buddleia can grow very tall. If your plant is rearing above your head, the few blossoms it does produce may be hard to see except from far away.
You can prevent this by giving your Butterfly Bush a hard pruning every one to three years. Get out your loppers in the early spring and cut the plant down to 12-24 inches in height. This will lead to a burst of new growth that can reinvigorate a Buddleia that’s aging and producing fewer blooms.
Trimming can also help if your Buddleia stops blooming earlier in the season than you’d like. In this case, instead of cutting the whole plant back, simply deadhead the spent flowers as they start wilting and going to seed. This increases the amount of energy and nutrients available for new blooms. Thorough deadheading can often extend the blooming season well into the fall while also giving the plant a neater appearance.
Problem #4: Swampy Soil
In some cases, Butterfly Bush bloom issues are really problems with the overall health of the plant. And one of the most reliable ways to make this shrub sick is to overwater it. When the roots are in a waterlogged, airless environment, they lose access to the oxygen they need, and they become vulnerable to nasty fungal infections.
This can happen because you’re watering your Butterfly Bush too often or because it’s planted in soil with poor drainage. Often, it’s a combination of both. Either way, you’ll see a similar constellation of symptoms. In order of increasing severity, they include:
- Soil remaining damp for days on end
- Stunted growth and flowering
- Drooping stems
- Rapid yellowing of leaves
- Brown spotting on foliage
- Widespread leaf loss
- Mushy spots on the stems
- Death of the plant
Mild cases may be fixable by simply watering less. Try holding off on giving your Butterfly Bush any water unless the temperature is above 90 degrees Fahrenheit or you’ve had several weeks with no rain.
If your plant still struggles to grow and bloom, you may have a drainage issue. Clay-heavy or compacted soil can take too long to dry out, causing problems even when you’re watering the right amount.
The only fix in that situation is to dig up the entire shrub and replant it. You can relocate it somewhere with better soil — see here for instructions on testing drainage. Alternatively, you can keep it in the same spot but make the planting hole a few inches shallower, covering the roots with a raised mound of earth. This makes them less prone to getting swamped.
Problem #5: A Dehydrated Butterfly Bush
Although overwatering is a more common problem, it’s possible for a Buddleia to get overly thirsty. When this happens too often, it can keep the plant from growing and blooming with its usual vigor.
It’s often easy to spot when your Butterfly Bush is getting thirsty. The foliage tends to wilt, becoming crispy and turning yellow or brown at the edges. The stems might also droop, especially the newer, more flexible ones.
You can correct an acute case of dehydration by giving your Buddleia a big drink of water. However, if you let it get to this point over and over again, you’ll continue to experience Butterfly Bush bloom issues. It may be helpful to rethink your watering habits if your plant keeps drying out.
Unfortunately, proper watering isn’t as simple as giving your Butterfly Bush a regular drink. Instead, you’ll have to pay attention to the weather conditions.
When you’ve gone more than a week with little rain and temperatures in the 90s, check on your plant’s soil. A moisture probe can give you an accurate picture of how dry it is. You can also get a rough idea by simply poking a screwdriver into the ground. If the earth is too hard and crusty for you to sink the tool more than an inch or two, it’s time to water.
Always make sure to drench the area around your Buddleia’s roots thoroughly. You don’t want to hydrate it too frequently, but you do want to give it a big drink when the time is right.
Problem #6: Pests Destroying Your Butterfly Bush Blooms
Several types of invading bugs can also interfere with your Buddleia’s flowering. Some attack the blooms directly, while others drain your plant’s juices, depriving it of important resources. Pest identification and control can depend a lot on the specific bugs, so we’ll profile the usual suspects:
Buddleia Budworm
These are actually caterpillars, the offspring of a drab and harmless-looking brown moth. They feast on the developing tips of Butterfly Bush branches, devouring leaves, and flower buds in their infancy. An infestation often leads to curled knots of shriveled foliage at the ends of new shoots. They may be wrapped in silky-looking webbing.
You can often limit the infestation by physically removing the caterpillars and squishing or drowning them. Spraying an organic pesticide made from Bt toxin can be even more effective. Just don’t do this when the plant is in bloom, or you could poison the butterflies that come to feed. Aggressively pruning your plant in the early spring can also remove the overwintering eggs before they hatch.
Japanese Beetles
Diagnosing a problem with these bugs usually isn’t hard. Their shiny green heads, bronze bodies, and fluffy abdominal hairs are quite distinctive, and they usually show up in swarms during mid-to-late summer. The damage they do is also very recognizable — they strip flower spikes bare and skeletonize leaves, eating everything between the veins.
This is another bug you can often remove by hand. Go out to your garden at night, pluck the sleeping bugs off the leaves, and drop them in soapy water. Spraying horticultural soap can also help (do this in the evening, too). Pouring some predatory nematodes into the soil may kill any grubs the Japanese Beetles have left behind.
Spider Mites
Spider mites are sap-sucking pests that tend to show up when the weather is hottest and driest, targeting thirsty plants. The foliage they’ve attacked will be speckled with tiny pale dots, and repeated feeding will make it yellow and withered over time. Spider mites also drape leaves and stems with cobweb-like threads that hold their eggs.
Horticultural soap can be an effective killer of spider mites, as can neem oil. Both should be applied after sundown because they make the leaves more vulnerable to sunburn. And both should be sprayed over the entire plant, including the undersides of leaves. Be prepared to apply multiple rounds of these treatments to fully rid your plant of mites.
Aphids
Like spider mites, aphids feed on the sap of your plant. They tend to clump around the tips of developing branches, attacking leaves and flower buds alike. They’re small but visible to the naked eye, resembling tiny blobs or bubbles of green, orange, yellow, or brown. You might also notice patches of the sticky slime they excrete.
A small infestation of aphids can often be kept from getting out of control by repeatedly blasting the bugs off the plant with a hose. If they prove more tenacious, you can usually get rid of them with the same pesticides we recommended for spider mites.
Problem #7: Fertilizer Overkill
Along with sunlight and water, Buddleias need nutrients like nitrogen, phosphorus, and potassium to bloom. But as with almost everything in the garden, it’s possible to have too much of a good thing. Overeager fertilizer application can lead to Butterfly Bush bloom issues.
This isn’t usually a problem if you stick to compost and mulch to enrich your plant’s soil. As they decay, these substances release nutrients at a slow, steady pace that’s perfect for a Butterfly Bush.
Problems can arise when you use synthetic fertilizers, especially those heavy in nitrogen. This can cause an overproduction of leafy growth as your plant tries to capitalize on the unexpected windfall. With most of the plant’s energy going into the foliage, flower production can be underwhelming.
Persistent over-fertilization — or a single especially large overdose — can lead to bigger problems. A high concentration of mineral salts in the soil can interfere with the root system’s ability to take in moisture. This can rapidly dehydrate your Butterfly Bush, leading to yellowing, curling leaves with blackened tips.
The best response to this issue is an extra-heavy watering to flush the extra salts out of the soil. In the future, it’s probably best to ease up on the fertilizer.
Final Thoughts
Most Butterfly Bush bloom issues can be traced back to a lack of something the plant needs to thrive. Whether it’s sunlight, water, oxygen, or room to grow, getting your Buddleia back to a healthy balance should help it resume blooming. You may have to wait until the next growing season before it fully recovers. But with time and proper care, the abundant flowering this plant is known for should return.