Are Butterfly Bushes thirsty plants? Watering is among the most important tasks in plant care, and it can sometimes seem like one of the trickiest. Ensuring that your Butterfly Bush gets enough moisture — but not too much — will go a long way toward helping it survive, bloom, and grow. Keep reading for a detailed overview of how to water your Buddleia.
You should water your Butterfly Bush thoroughly but not too frequently. During dry weather, test the soil and hydrate it if the top two to four inches are dry. In the first year after planting a Buddleia, you’ll probably need to water it more. Give it a drink if you get less than an inch of rain in a week.
Part of what makes a Butterfly Bush such a great landscape plant is that it’s tough. Once your shrub is well-established, it should be able to handle occasional droughts fairly well. And you can help make it even more resilient and easy to hydrate by planting it correctly. We get into even more detail below as we explain when and how to water your Butterfly Bush.
How Much Water Does a Butterfly Bush Need?
As a rule, Butterfly Bushes aren’t particularly thirsty. They’re known for their ability to grow in thin, marginal soil and disrupted ecosystems — in post-WWII England, they earned the nickname “the bomb site plant”. Their favorite environments are riverbeds and floodplains with well-drained soil that dries out quickly between the occasional deep drenches.
A Butterfly Bush will grow and flower best when its roots remain lightly moist most of the time. It can tolerate short droughts once established, though it may not bloom as much if it dries out frequently.
Wet, clingy soil is a much bigger problem. Butterfly Bushes are highly susceptible to root rot, a nasty disease that can be caused by a variety of soil microbes.
Under normal conditions, these fungi and bacteria don’t bother your plant. But when the soil gets waterlogged and low on oxygen, the wrong kinds of microorganisms begin to breed like crazy. They can overwhelm and begin to devour a Buddleia’s roots. This means it’s usually better to water a Butterfly Bush too little than too much.
Soil Quality and Butterfly Bush Watering
Technically, you’re never actually watering your Butterfly Bush — you’re watering the ground where it grows. You’ll have a much easier time keeping it hydrated if you’re conscious of the soil it’s planted in. It’s much easier to drown the roots if they grow in heavy clay loam, where water pools and puddles after every rainstorm. And it’s much easier to let them get dehydrated in loose, rough sand.
Testing the Drainage
Here’s a simple method you can use to test the drainage of your soil:
- Dig a hole. It should be one foot deep by one foot wide. Dig as close to your Butterfly Bush as you can get without disturbing the roots. It’s even better if you can do this before planting in the exact spot where you want your shrub.
- Soak the soil. Fill the hole with water and let it sink in until there’s no more standing water.
- Fill it up again. Once the hole is empty, fill it to the top. Now that the sides and bottom are wet, you can be sure you’re measuring drainage, not absorption.
- Track how fast it drains. Get a ruler or tape measure and check the depth of the water once an hour until the hole is empty again. Then average out the readings to get the rate of drainage.
The ideal drainage rate for a Butterfly Bush is between one and three inches per hour. If it’s faster, you might need to keep a closer watch on your plant during the summer to make sure it doesn’t get dehydrated. A slower drainage speed means it’s at greater risk of overwatering.
Fixing Overly Fast Drainage
You can help correct for fast-draining soil by adding some mulch around the base of your Butterfly Bush. This will help in the short term by decreasing the rate at which the soil loses moisture to evaporation. And in the long run, it will add organic matter to the earth as it decomposes. This squishier, stickier material will retain moisture better.
Our preferred mulching method is to lay down a two inch layer of compost followed by a two inch layer of wood-based mulch. Leave a buffer of a few inches between the mulch and the stems of your Butterfly Bush. The mulch should extend out as far as the branches do, or possibly an inch or two farther.
Note: though you might be tempted to mix the compost or mulch directly into the soil before planting, this is usually not a good idea. When the soil is much richer near the base of the plant, the roots are less likely to extend out. This can be bad for your Buddleia’s health in the long run. Mulching on the surface allows organic matter to infiltrate the soil slowly and evenly.
Fixing Overly Slow Drainage
If your soil drains too slowly, adding organic material can also improve it over time. You’ll have to be more careful, though, because too much mulch could make the soil stay waterlogged even longer. We’d suggest laying down a two inch layer of compost but skipping the woodier mulch.
Again, you should avoid amending the soil directly, which can do more harm than good. However, planting (or transplanting) your Buddleia slightly above the soil line could help keep its roots out of standing water. You can find instructions in this article.
How to Water Your Butterfly Bush
The best way to water your Butterfly Bush is infrequently but deeply, and only during hot weather. Throughout the growing season, you can test the soil once per week. If the upper two to four inches are dry, your Buddleia needs watering.
A soil moisture meter is a good tool for this purpose. You can also use the “screwdriver test”: if you can’t easily push a screwdriver more than a few inches into the ground, it’s time to water. (This doesn’t work as well in sandy, naturally loose soil.)
When you find that the ground is dry, give your Buddleia a nice long drink. When using a
You don’t need to worry that you’ll overwater your Butterfly Bush this way. That happens when you give it water too often, not when you add too much at once. Testing the soil first should ensure that you avoid this mistake.
The best time to water a Butterfly Bush is in the morning. This will help keep its roots cool throughout the day. It also allows time for some of the moisture to evaporate before sundown, reducing the chances that your Buddleia will sit in swampy soil.
Watering a Newly Planted Butterfly Bush
The above advice should work well for a Butterfly Bush that has settled comfortably into your garden. But if it’s been less than a year since you planted it, you’ll need to be a bit more proactive about watering. Your Buddleia’s root system is still in the process of growing out and digging in.
During the first spring and summer after planting, pay attention to how much rainfall you receive. If you get less than an inch in a week, water your Butterfly Bush well to make up the difference. Once again, water for a long time, letting it soak deep into the ground.
Factors That Can Affect Watering Frequency
Naturally, you’ll have to adjust your watering habits based on your particular plant’s needs. Here are a few factors to consider:
- How well the soil drains. If it’s naturally dense and tends to form puddles after rain, you can probably go a bit longer without checking on it. Fast-draining soil, on the other hand, should be checked weekly during the growing season.
- Your Butterfly Bush’s light exposure. These plants typically prefer full sun, which spurs fast growth and lots of blooming. But this also means they use more water, and the soil dries out more quickly. Test the soil more often in sunny spots than partly shady ones.
- The weather. If you’ve been getting heavy rain, there’s no need to water your Butterfly Bush at all. In extended periods of hot, dry weather, you’ll need to watch more carefully for signs of thirst.
How to Tell if Your Butterfly Bush Isn’t Getting Enough Water
Mistakes are a fact of life in gardening, and there will almost certainly be times when you mess up your Butterfly Bush’s watering schedule. This is even more likely when you’re still getting used to its needs. How do you know if your Buddleia is becoming dehydrated?
Slow growth and failure to produce many blooms can be important signs. A Buddleia, like any plant, needs water to support photosynthesis and growth. If it seems to be sluggish despite getting plenty of sunlight, it could be that you’re watering it too sparingly.
When healthy, these plants put on about four to six feet of growth in a typical season. If yours is gaining noticeably less, consider checking the soil moisture levels more often. Note that this growth rate may be lower for dwarf cultivars.
An urgent shortage of moisture will often be accompanied by wilting foliage. The leaves will sag and may turn yellow and/or brown. They’ll often shrivel up and take on a crispy, papery texture. Keep in mind that it’s normal for this to happen in the fall, as your Butterfly Bush is a deciduous shrub.
The fix is simply to water your Buddleia thoroughly and keep a closer eye on its hydration needs in the future. It will most likely bounce back once you’re watering it properly again. The damage to the leaves won’t go away until they drop off in the autumn, and you still might not see as much blooming this year. However, your Butterfly Bush should stop wilting and resume growing once you quench its thirst.
How To Tell if Your Butterfly Bush is Overwatered
What if you’re worried you’ve drenched your Buddleia too much? Unfortunately, the symptoms can be quite similar to the signs of underwatering. That’s because the roots of an overwatered plant start to suffocate from the lack of oxygen in the soil. As a result, the upper parts become dehydrated.
There are a few differences to watch out for, though. Take a look at the newer growth on your plant. When a Butterfly Bush is overwatered, the fresh leaves and flower spikes are often smaller than normal.
Also, the wilting leaves may have a soft, limp texture rather than feeling brittle. The stems might be soft and weak, too, making it hard for them to support the weight of their blooms. In severe cases of overwatering, you may notice leaves and flowers dropping off and stems dying back.
When you’re trying to tell if your Butterfly Bush is overwatered or underwatered, you should always check the soil. If it’s damp, you can be pretty sure your plant isn’t thirsty. And if the ground is caked and dry, you can usually rule out overwatering. Consider your care routine, too — if you’re watering every day, it’s a lot more likely that you’re drowning your Butterfly Bush than drying it out.
You can’t do much about overwatering except let the soil dry out and hope that your Buddleia recovers. If you notice soft and mushy spots on the stems, prune them off so the rot can’t spread. Make sure to disinfect your pruning shears or loppers before every cut.
Additional Tips for Watering a Butterfly Bush
Here are a few more things to keep in mind when you water your Butterfly Bush:
Potted Butterfly Bushes Need More Water
We’ve been talking about Buddleias grown as landscape plants, but what if you’re raising yours in a container? In that case, you’ll have to be mindful of the fact that it’s working with a much smaller amount of soil. This makes it more vulnerable to both underwatering and overwatering. There’s not as much earth to soak up excess water, but there’s also not as much soil mass to retain moisture between waterings.
What all this means is that you’ll need to be diligent about checking your Butterfly Bush’s pot. Test the soil every few days during the summer, even if it’s rained recently, and continue checking weekly, even during the fall. If the soil ever seems visibly damp for more than a few days in a row, you might need to replace it with a coarser potting mix.
Watch Out for Hydrophobic Soil
Some soils can become hydrophobic if they get too dry, developing an oily coating that repels water. This is more common if the soil is sandy or contains a lot of organic matter that hasn’t decomposed enough. It can be difficult to properly water a Butterfly Bush once this happens because the liquid tends to bead up and roll away.
Mulching can help by locking down the moisture long enough to let it drain into the soil. Slow, steady drip watering may also work. If that doesn’t do the trick, you can add a few drops of gentle soap to a watering can. This will counteract the water’s tendency to slide off the soil surface.
Buckets, Not Sprinklers
Let’s talk about the tools you can use to water your Butterfly Bush. We’ve already mentioned
To use this method, just drill a small hole in the bottom of a five gallon plastic bucket. Set it down near your Butterfly Bush, fill it up with the hose, and let the water slowly trickle out. You might want to move it around to different spots a few times as it drains to get the roots evenly soaked. The bucket method helps the water permeate the ground slowly instead of pooling up and running off.
If you’re using a lawn sprinkler, remember it may not water deeply enough for a newly planted Butterfly Bush. You’re often better off using one of the other watering tools described above. Even once your plant is established, you may not be able to rely on a sprinkler alone to water it. Test the ground after running it to make sure it’s thoroughly soaked and not just moistened at the top.
Final Thoughts
Water your Butterfly Bush deeply, but only when the soil is getting dry. Remember that getting to know your soil is an important part of proper watering, so test the drainage and adjust accordingly! If you stick to that approach, you should be able to keep your Buddleia well-hydrated and living its life to the fullest.