I’m sure you’ve seen them in the garden center. You may have just thought they were mini-petunias like I did when I first saw them. Calibrachoa, also called Million Bells, or known by the brand name Superbells, are a plant that I love more and more each year that I use it.
Calibrachoa, like petunia, is a genus in the Solanaceae family. This means they are related to other more well-known Solanaceous plants deadly nightshade and tomatoes. Initially, Calibrachoa were considered to be just another species of petunia. After all, they do look like tiny petunias.
There has been a lot of debate in the botany world about whether Calibrachoa is its own separate genus or not. Modern DNA marker analysis, like what we see on TV shows like CSI, supports the idea that Calibrachoa are a different genus. Research published in 2005 looked at DNA fingerprints of all known species of petunia and Calibrachoa and statistically measured how much of that fingerprint was shared among species. Their results showed Calibrachoa was a separate group from petunia, which suggests Calibrachoa is a different genus.
Calibrachoa is native to South America, just like its cousin petunia. In its native land, Calibrachoa is a weak evergreen perennial. It can survive winters in hardiness Zones of about 8 or 9. In many parts of the world, Central Illinois included, Calibrachoa is grown as an annual.
Europeans knew about Calibrachoa about 200 years ago thanks to explorers of the New World. They didn't catch on and existed mostly unchanged until a Japanese company called Suntory started experimenting with hybridizing them in the late 1980’s. The first hybrid cultivars came on the gardening scene in the early 1990’s. Nearly all of the Calibrachoa available in stores today are hybrid cultivars, most from Suntory.
I had never heard of this company before writing this article, but some internet searches revealed they are breeders of many different annual bedding plants. Their plants dominate the market in Europe. They also hold many patents on their hybrids.
Penn State University has tested hundreds of Calibrachoa hybrids in the field and found that breeders are making real improvements in more compact plants, season-long flowering, flower color, size, and form. Another significant trait Penn State highlights is that the newer cultivars are more resistant to root rots, which can be a problem in Calibrachoa. Their observations suggest it may be worth your while to try the latest Calibrachoa cultivars available.
Calibrachoa plants look for all practical purposes like a petunia plant in miniature. Their leaves are pubescent (hairy), and flowers are trumpet-shaped, about one inch in diameter. The flowers range in color from red to pink, magenta to blue. What I find unique is there are a lot of bronze, orange and yellow cultivars, colors you don't see very often in petunia. I’ve seen a few yellow petunias, but not orange and bronze ones.
The growth habit of Calibrachoa varies. I love them in hanging baskets. They are great “spillers” cascading over the sides of a pot. Some cultivars are more upright and spreading, reaching a height of ten to fifteen inches, while others are more trailing or sprawling, and only reach of height of four to six inches.
A sunny spot in the garden is best for Calibrachoa. The more partial the sunlight, the fewer flowers they produce. They will flower best in a sunny location with periodic applications of fertilizer through the growing season. They also do best in acid soil less than a pH of 6.0.
Calibrachoa needs well-drained soil where ever its planted. They do not like wet feet and may tend to develop root rot. The good news is they do tolerate drought well, so if our summer ends up hot and dry, this shouldn't be a problem. Do keep a careful watch on plants in containers though, as containers can dry out way too much even for drought-tolerant plants in our summer heat.
You may wonder like I have, why all the Calibrachoas in stores are more expensive than the average petunia. I’ve never seen them sold in flats, but always in three or four-inch pots at a premium price.
According to the Missouri Botanic Garden, Calibrachoa produces very little seed, making it impractical for producers to propagate them by seed. Instead, they must be propagated using cuttings from existing plants, which costs more in time and labor. So they might as well put them in pots rather than flats. This translates to a higher cost to the consumer.
Even though they do command a higher price, I have been using Calibrachoa more and more in my garden each year. The plants produce tons of flowers—you get a lot of bang for your buck. I use them primarily in containers, but they will grow well in the ground too. If you haven’t tried Calibrachoa, I highly suggest you grow at least one this year. My bet is by the end of summer you’ll be wishing you planted more.