Seven Reasons To Not Plant The Butterfly Bush

The Butterfly Bush is one of the most popular flowering shrubs in suburban landscapes, and it is easy to see why. It has a long bloom period of showy flowers. These flowers produce lots of nectar that in-turn, attract butterflies. And finally, it is very adaptable, able to grow in a variety of conditions (and has established itself in the wild)^[1]. But these benefits come at a cost to local ecosystems, which I will describe in this article.

Before I go into the details we must never forget – nature is a complex system, and small changes can have large second or third order effects. The replacement of native flora with the invasion of the Butterfly Bush has many negative consequences for our local ecosystems that I will describe. Some of may not even have been seen as of today, as it can take decades for the changes to truly manifest themselves. And as nature is a complex system, out of caution we should follow the principal “first, do no harm”, especially with plants that have the ability to spread on their own.

Background

First brought over from China, where it is native, the Butterfly Bush is frequently sold in stores as a plant that will attract numerous butterflies (which it does)^[2]. It does not however, provide any hosting for native butterflies or moths. Now, considering most suburban gardens grow exotics rather than natives (something we’re trying to change), the butterfly bush may not seem like a big deal. But it is.

The problem of the Butterfly Bush has been recognized by many states where it is listed as noxious and invasive^[1]. And despite being a foreign plant, it has established itself in numerous states in both the East and Western United States.

How the Butterfly Bush harms native ecosystems

I’m going to walk you through the advantages the Butterfly Bush has over native species, but I’ll list them in order for you here, as when you combine them all it makes for a terrible situation for natives:

1. Reduced nectar quality
2. Self-seeding (How it spreads)
3. Deer won’t eat the Butterfly Bush (probably the most important)
4. Fast growing / adaptable
5. Crowding out native plants
6. Reduced habitat for butterflies and moths
7. Roots damage foundations and walls

1 – Nectar properties

The nectar of the Butterfly Bush has a high enough concentration of sugar to attract butterflies, and each mature plant produces lots of flowers. It has been measured to be between 17-33% and each nectary producing between 0.36-0.64 micro-liter^[3]. Now, this amount of sugar is less than many comparable native flowers (see table below). So, while the sugar content combined with the quantity of flowers is high enough to attract butterflies, they will receive less energy for the amount consumed.

Scientific Name	Common Name	Mean Sugar Concentration	Average Amino Acid Concentration (ng/μl)
Asclepias incarnats	Swamp Milkweed	58.96	121.28
Asclepias syriaca	Common Milkweed	37.66	78.80
Asclepias tuberosa	Butterfly Milkweed	57.23	66.01
Coreopsis lanceolata	Lance-leaved Coreopsis	33.6	146.63
Coreopsis tripteris	Tall Coreopsis	53.73	253.87
Eupatorium purpureum	Joe-Pye Weed	31.54	55.73
Helianthus giganteus	Giant Sunflower	47.23	255.65
Liatris aspera	Rough Blazing star	59.75	46.87
Liatris spicata	Dense Blazing star	49.52	78.34
Monarda fistulosa	Wild Bergamot	56.12	52.59
Monarda punctata	Spotted Bee Balm	61.28	14.00
Symphyotrichum novae-angliae	New England Aster	51.81	138.16
Vernonia gigantea	Tall Ironweed	44.84	255.69

Now, there are other compounds within nectar that are necessary for the health and nutrition of our native pollinators. For instance amino acids are critical to the survival of migrating Monarch butterflies. I have not found any studies analyzing Butterflybush nectar that have identified these compounds[4].

When these factors are taken as a whole, the lower sugar concentrations in the nectar of the Butterfly Bush means that butterflies will need to consume more of it to receive the same energy as they would from natives whose nectar has higher sugar concentrations. Also, there are some studies that specifically note amino acids as very important for survival of various butterflies such as Monarchs. As of now I haven’t been able to find any amino acids detected in Butterfly Bush nectar from the studies that I could locate.

The fact remains, that while our native flora evolved with our native butterflies, the Butterfly Bush did not. Thus it’s likely that it’s nectar properties were selected (via evolution) to best satisfy pollinators native to China. And while there may be significant overlap in what all butterfly species need (sugar, for example), we cannot say that our native butterflies will receive all their necessary nutrition from nectar of a foreign flower.

2 – Self-seeding

The numerous flowers seeds by a healthy, established butterfly bush can spread via wind or floating on water to other wild areas and colonize the ecosystem. And while it may not seem invasive in your own yard, seeds that spread to wild or unattended areas that you don’t control can easily begin new colonies. Look, I’ve never grown this plant, but have pulled them from my yard. They do spread, and will spread whether you see them or not.

Another note – all this talk of nectar in the previous section doesn’t mean butterflies aren’t attracted to this plant – quite the opposite. That is one of the primary reasons it is popular in suburban landscaping…it does attract butterflies. But, this also allows for cross pollination[5], which is necessary for the plant to spread.

And if you are unsure of just how much this plant will self seed….have a look below. These are some images showing different places that it has successfully established itself. Some of the images even show it growing in walls!

3 – Deer won’t eat them

This is the single biggest reason the Butterfly Bush can out-compete natives. Just about all of our native shrubs and flowers can be shaded out by other trees and shrubs, native or not. However, the Butterfly Bush has a comparative advantage over our native vegetation- deer won’t eat the Butterfly Bush (an advantage shared by the Bradford Pear tree). That alone is probably the biggest advantage the Butterfly Bush will have over native shrubs.

Deer not eating an exotic species, while consuming saplings and young native shrubs will give the exotic a HUGE advantage. It is basically like having deer mow the vegetation surrounding a Butterfly Bush, but leaving it in-tact. By not having it’s leaves eaten, it can therefore receive more sunlight and simply outgrow natives.

4 – Fast growing and adaptable

Butterfly Bush grows rapidly in full sun and medium-moist to moist soil that drains well. And it can keep pace, or out-pace most other native species. This again, combined with deer not eating them means they will out-compete natives over time (which they do, particularly in disturbed areas).

5 – Crowding out natives

And this is where it displacing native vegetation is a concern, as butterflies and moths will only lay eggs on specific species. If these species die out in competition with a faster growing shrub such as the Butterfly Bush, the local ecosystem will suffer as there won’t be more butterflies.

For a specific example of this, take the Spicebush Swallowtail butterfly. It will happily feed on nectar rich flowers such as the Butterfly Bush. But, it will only lay eggs on the Spicebush, and no other plant. What this means is that fewer Spicebush shrubs will equal fewer Spicebush Swallowtail Butterflies.

Now, consider other native populations that can be displaced or crowded out by the Butterfly Bush. It won’t just be other shrubs like Viburnum, Button Bush or Winterberry. We can also add regular herbaceous species (flowers that die back to ground in winter) to the list such as Milkweeds, Echinacea, Liatris, or Ironweed.

6 – Reduced habitat for native butterflies and moths

Our native butterflies and moths will only lay their eggs on specific species of plants, and the Butterfly Bush is not one of them. Thus when the Butterfly Bush begins to spread in a local wild area, which it will do via a lack of deer predation combined with fast growing and being quite adaptable, the final result is fewer native flowers and shrubs. This means less hosting capacity of native butterflies and moths.

7 – Roots from Butterfly Bush can damage walls

The roots of some plants can damage walls and foundations, and Butterfly Bush falls into this category. In fact, it is one of the ways it naturalizes itself to an area is that it seems to grow very well in crags of rock and quarries (see Great Britain in the 1930’s)^[8]. But these roots, as they grow they will increase in diameter. As the diameter increases it will place stress on the masonry, brick, or foundation. Couple this with any freeze/thaw cycles, and you have a recipe for future structural problems.

Now, you may be a well informed gardener who knows this and thus avoids planting one too close to a foundation. But – remember, this is an invasive plant that spreads easily! So, if your not careful you may have a new surprise plant that you didn’t plant showing up next to a wall!

What you can do to help

If you already have a Butterfly Bush in your yard, there are several ways you can help:

1. Remove the Butterfly Bush from your yard
2. If unable to remove, simply cutoff and remove any spent flowers (deadheading)
3. Only purchase sterile cultivars (risk of spreading isn’t totally eliminated)
4. Plant native alternatives

Removing a Butterfly Bush

First, it would be best to remove it to eliminate any risk of it spreading. And that is what I would absolutely do in my own yard were one present. Note that any/all branches should be burned or disposed of in trash bags, and due to their ability to re-sprout should not be composted (unless your compost pile gets hot enough to kill them).

Now, the roots have the ability to re-sprout new shoots. So, you’re going to have to either dig out the entire root system, which is a big job, or kill the stump. I have a virtually full-proof system to killing stumps to stop them re-sprouting.

Deadheading spent flowers

However, if you do have an established Butterfly Bush and can’t bear to part with it, you can at least deadhead and remove all spent flowers to eliminate the risk of self-seeding. This may seem like a bit of a job, but at least there won’t be a risk of creating a new population outside of your property.

Only growing sterile hybrids

Finally, if for some reason you feel you absolutely have to have a Butterfly Bush, purchase one that is sterile, or nearly sterile. For instance, although the Butterfly Bush is listed as noxious and invasive in Oregon, the states department of agriculture did approve certain cultivars to be sold, provided that they were sterile or nearly sterile (<2% of seed viable). See list below for more types that are less risky.

Species	Cultivar Name
Buddleja	‘Asian Moon’
Buddleja	‘Blue Chip’
Buddleja	‘Blue Chip Jr.’
Buddleja	‘Ice Chip’
Buddleja	‘Inspired Pink’
Buddleja	‘Lilac Chip’
Buddleja	‘Miss Molly’
Buddleja	‘Miss Ruby’
Buddleja	‘Miss Violet’
Flutterby GrandeTM	Blueberry Cobbler Nectar Bush
Flutterby GrandeTM	Peach Cobbler Nectar Bush
Flutterby GrandeTM	Sweet Marmalade Nectar Bush
Flutterby GrandeTM	Tangerine Dream Nectar Bush
Flutterby GrandeTM	Vanilla Nectar Bush
Flutterby GrandeTM	Snow White Nectar Bush
Flutterby GrandeTM	Pink Nectar Bush

Plant natives instead

And finally, plant an alternative to the Butterfly Bush. There are numerous species of native plants that can provide all the same benefits of a Butterfly Bush, but won’t have the risk of harming the local ecosystem.

Some alternatives that bloom at the same time would be Buttonbush or Sweet Pepperbush. While others that bloom earlier would be Spicebush, Blackhaw, or one of our many native Dogwoods. These have the added benefit of attracting birds to your yard as well.

Final thoughts

The Butterfly Bush has been one of the most popular shrubs sold by nurseries for many years. And, it is easy to see why. They are showy, adaptable, and they do in-fact attract butterflies^[7]. But these negative consequences of this shrub to local ecosystems is real, and like all invasive plants, a self-multiplying problem that only gets bigger with time.

Harm caused by the Butterfly Bush is significant, and we can see the first, second, and even third order effects. First order effects are less energy in the nectar. The first second order effect is less caterpillar larvae habitat from crowding out natives. And this leads to a third order effect of less food for birds as many species eat hundreds of caterpillars a day for themselves and their young.

If one feels they must have this plant, then they should take care to only have a sterile variety, or dead head every spent flower to prevent the spread outside of their yard. Although the better solution would be to remove the plant and replace it with native alternatives that are purely beneficial to your environment, rather than harmful.

Read more about Invasive Plants here