Jennifer Schultz Nelson
Extension Educator, Horticulture
A plant that I love, but that tries my patience is Butterfly Bush, Buddleia davidii. While it is a pretty common shrub in central Illinois, that is not the case everywhere.
When I started graduate school ten years ago, I remember seeing Butterfly Bush and asking people what it was and getting strange looks in return. I don't remember having this plant at home while growing up, probably because it can have a hard time with cold northern Zone 5 winters typical of the Chicagoland area where I grew up.
The genus Buddleia (originally spelled Buddleja ) was named after a British botanist and clergyman named Reverend Adam Buddle. There are about 100 different species in this genus, native to many different warm parts of the world. Butterfly Bush may seem commonplace and even boring to some, but the species most often grown in this area, Buddleia davidii is actually an exotic import not native to North America. It is native to China.
The species name davidii in Buddleia davidii was given in honor of plantsman Armand David, who discovered the shrub in China. This particular species has been bred extensively and the wide variety of cultivars available is no doubt part of what makes it a very popular landscape plant.
Another reason for its popularity is a dead giveaway in Buddleia davidii's common name Butterfly Bush–this plant is an absolute butterfly magnet. It is not uncommon to see one bush harboring several different species of colorfully winged visitors all at the same time. The pendulous clusters of tiny orange-throated flowers that look somewhat like small versions of lilacs are attractive to humans too. They also have a very pleasant scent reminiscent of lilac, which is the origin of another of its common names, Summer Lilac.
While I admired the plant in graduate school, I didn't have an opportunity to plant my own Butterfly Bush until I was a homeowner. Everything I read about them had said they love full sun and while they prefer well-drained, fertile soil, they can adapt to poor soil. They are also tolerant of heat and humidity. Living in a new subdivision, I needed all the full sun, poor soil tolerant plants I could find!
The mail order catalogs I poured over that first year showed pages and pages of various shades of purple, blue, pink, red, white, and even a yellow cultivar called 'Honeycomb', but the cultivar 'Bicolor' caught my eye and I was in love.
The flowers of 'Bicolor' change color with age. The flowers start out a vivid pink-purple color and slowly turn to a butterscotch yellow. At any given time there are two completely different colors on the same plant! The very first mail order I assembled for my brand new landscape contained one Buddleia davidii 'Bicolor'. And a huge trial of my persistence and patience was born.
The plant that arrived was potted, and fairly small, which is typical of how I like to garden. I prefer to spend my money on small plants and have a lot of different ones to plant and watch grow. I planted my 'Bicolor' Butterfly Bush that spring and eagerly waited for its colorful blooms. Within two weeks the plant was clearly dead. I called the company to ask for a replacement, and they couldn't send one until fall. The operator advised me that I might still get some shoots to regrow if I watered well. I watered well but no shoots ever appeared.
What the operator at the mail order company told me was not just a lie to get me off the phone. Most books and other references categorize Butterfly Bush as a shrub, but in Zones 5 and 6 it typically dies back to the ground each winter much like an herbaceous perennial. New growth emerges from points just beneath the soil surface.
Judging by how big a Butterfly Bush can get in a single season, its growth rate makes up for lost time each year despite dying back to the ground in our Zone 5 climate. Many cultivars routinely achieve dimensions of five feet tall and wide. Often times the previous year's growth is quite extensive and woody. One person told me they have to use a small chainsaw to remove the previous year's growth of their Butterfly Bushes each spring!
In a warmer climate where they don't totally die back each winter, Butterfly Bushes routinely get to be eight to ten feet tall. In some warmer climates Butterfly Bush's vigorous growth and ability to spread via seed has earned it the title of being somewhat invasive.
Despite this invasive reputation in some climates, I have yet to successfully overwinter a Butterfly Bush in my own backyard. I have replanted 'Bicolor' twice without success. I had great success last summer with a mystery purple-flowered cultivar that was mislabeled as 'Bicolor' but was covered in dozens of deep purple blooms at a time.
I thought sure this mystery cultivar would survive. Despite starting out in a four inch pot, it was easily five feet by five feet by summer's end. I had planted it near the house for a little extra protection. I mulched it carefully over the winter, and crossed my fingers. In the spring I eagerly awaited any sign of life, realizing that Butterfly Bush is routinely one of the last plants to wake up in the spring. Nothing ever grew.
I eventually dug around the remains of the Butterfly Bush to try and figure out what caused its demise. I never did find any clear reason. It was very well established, as evidenced by tons of roots that in some cases were about ten feet long.
I am not ready to give up yet though. Maybe I just haven't found the perfect spot yet. I purchased six different Butterfly Bush cultivars this year and placed them in different spots to see if I can find a survivor among them.
I planted a semi-dwarf cultivar, 'Nanho Blue' early this spring, hoping that the early start would help it establish itself firmly in my landscape. The typical Butterfly Bush is very open and airy, sometimes even leggy. But 'Nanho Blue' has a much fuller growth habit, and is of course a bit shorter. It is going strong next to my patio, and covered in blue flowers. So far, so good.
To combat the sometimes spindly growth habit of non-dwarf type Butterfly Bush, some sources recommend lightly shearing back the plant early on in the season before blooming starts. This encourages the plant to branch and ultimately each branch will produce more flowers, since Butterfly Bush flowers on new growth. Deadheading to remove old flowers regularly will also encourage more flowers to develop.
I planted the other cultivars in June, and they appear to be thriving. If you're curious, I planted: a deep purple cultivar called 'Black Night', a light pink named 'Pink Delight', a "red" cultivar that looks purple to me called 'Royal Red', a light blue cultivar 'Orchid Beauty', and a deep blue 'Empire Blue'. These are all pretty commonly available cultivars that I found for less than $5 each locally. Until I figure out some way to overwinter them, I don't want to spend more on a newer cultivar.