Top 10 Questions About Butterfly Bush

By Teo Spengler | April 26, 2020
Image by TracieMichelle
by Teo Spengler
April 26, 2020

It’s hard to find a shrub that is easier to care for than butterfly bush, and I, for one, never have. Those gracefully arching stems hang heavy with cone-shaped flowers in wonderfully rich shades of blue and purple the entire growing season with very little effort on your part. But that doesn’t mean you won’t face challenges, especially when you are just getting started with these vigorous shrubs.

That’s why it is the goal of Gardening Know How to provide the best information possible so your garden will flourish – and that includes answering whatever gardening questions arise. In this article, I’ll tackle the top questions readers have asked about growing butterfly bushes in the garden.

1. When is the best time to move a butterfly bush?

Transplanting a deciduous bush of any kind is usually easiest in early spring or late fall and butterfly bush is no exception. Your best choice will depend on your climate. Spring works better for gardeners in colder regions since the new transplant will have a warm summer in which to establish in the new location. Autumn is a better option for hot-summer states.

2. How should butterfly bushes be pruned?

I’m crazy about butterfly bushes. They were among the first flowering ornamentals I planted in my yard in France, and, despite cold winter and months at a time when I’m not even there, they are among the fullest, healthiest shrubs around. These are such easy plants that ordinary, cautionary rules don’t apply. It is virtually impossible to do anything that will dent the energy or enthusiasm of these guys by bad pruning. If you want them smaller, prune off each stem, making the cut just above a bud. It you want a different shape, go for it. I prune my butterfly bushes whenever I get back to France, sometimes in spring, sometimes in winter, once even in mid-summer. And they keep right on blooming.

3. What to do for butterfly bush turning yellow?

Whenever I see a shrub’s leaves turning yellow, I think of the yellow on a traffic light that tell you to be careful, that things are about to change. Yellowing leaves on a plant are also an indication that it’s time to be more careful with some aspect of plant care, usually irrigation. It is likely that a butterfly bush turning yellow is either getting too much water or too little. You’ll probably know right away which one is more likely. Don’t forget that too much water may have more to do with the soil than with how much water you are pouring in. These plants don’t need much to be happy, but they absolutely do need one thing: good drainage. If you stick one in a pot without enough drain holes or soil that holds water all too well, it’s time to make a change!

4. How do you get rid of pests on butterfly bush?

The insects you are most likely to see on butterfly bush are butterflies, but of course, attracting the flutter-bys is why we plant the shrubs in the first place, right? The truth is, butterfly bush is such a tough plant that I personally haven’t dealt with any pest issues. If you live in a dry climate and your shrubs get water stressed, spider mites can appear. You’ll recognize them by the little webs they construct. A jet of water from the hose will both remove the mites and provide the plant with water. If not, bring out the neem oil spray.

5. Can butterfly bush be grown in a container?

This is kind of like asking if you can keep an elephant in a box. That answer is yes, if you are sure you want to. Butterfly bush is one of the most vigorous plants around, so much so that it is considered invasive in many areas. The shrub can grow twice as tall as you are and expand to 15 feet (4.5 meters) wide. If you want to grow it in a pot, pick a very large one (like half a whiskey barrel), select a dwarf variety of the shrub and provide top-notch drainage.

6. When and how to deadhead butterfly bushes?

Deadheading means chopping off flowers when they fade. With butterfly bushes, the flowers just keep on coming, so you’ll have your work cut out for you. But the technique isn’t anything special; just use sharp, clean pruners to snip off each browning flower head. Make the cut at the branch point where there are other flower heads branching off.

7. How do you propagate a butterfly bush?

With butterfly bush, you’ll have lots of options when it comes to propagation: seeds, division of the clump or rooting cuttings. I like cuttings best because they are more reliable and faster than seeds and much easier than digging up the entire clump to divide it.

How to propagate with cuttings? Clip off branch tip cuttings in spring or summer, making each one twice as long as your longest finger. Trim off the bottom sets of leaves, cut the bottom on an angle, then stick it into a small pot of moist potting soil. Keep it in a well-lit area but out of direct sun until you see new growth indicating that roots area developing.

8. How do you plant a butterfly bush?

Take the time to find a good location when you are planting a butterfly bush. That will save you untold effort in the future since a good planting site means almost zero maintenance. Pick a sunny spot (you do want flowers, right?) with fertile, well-draining soil. Make sure that there is enough room for the plant to spread out when it is mature. If you don’t do this, you will be forever having to cut it back. Don’t fertilize.

9. Why didn’t my butterfly bush produce flowers?

No sun, no blossoms. It’s as simple as that. This is the most common reasons or a butterfly bush not blooming. If you missed the part about planting the butterfly bush in the sun, no problem. Just go back and reread the part about transplanting a butterfly bush. And get it in the sun this time.

10. How to overwinter potted butterfly bush plants?

Butterfly bush is a tough plant. If you have a potted butterfly bush, however, it is your job to make sure that your winter isn’t tougher. Overwintering is easy in mild climates, where an extra few inches of mulch is all you need. In areas where temperatures fall noticeably, move the pot into a spot that is sheltered from winter winds. These shrubs are very cold hardy, but if you live in USDA zone 4 or colder, you’ll need to overwinter the container shrub inside a garage or closed porch. If you don’t have either, dig a hole in the ground and put the butterfly bush container in it, cover it with soil and add a thick layer of mulch. If you are worried about heavy snow or ice storms breaking the plant stems, prune them back by half or even more. This won’t stop them from flowering again the following spring.

We all have questions now and then, whether long-time gardeners or those just starting out. So if you have a gardening question, get a gardening answer. We’re always here to help.

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