Modern breeding of Buddleia began in 1900. Naturalist E.H. Wilson made germplasm collections of Buddleia davidii from western China while traveling for the Veitch nursery in London and the Arnold Arboretum. The material sent to Celine Boston this plant nursery formed the basis of the modern garden hybrids. In 1914, Mr. Van de Weyer created Buddleia eyeriana which is still popular today.
Today, there are several prominent Buddleia breeders. New cultivars are being announced every year by breeders and plant nurseries. The new cultivars offer novel combinations of plant height, leaf color and flower color. Flower color varies along a continuum and include shades of white, blue, purple, pink, orange, and yellow. Although there are cultivars that claim to be red, they are really reddish-purple. Panicles vary in shape from narrowly cone-shaped to fat and round. A few cultivars have flowers with branched panicles. Newer cultivars tend to be sterile or have vastly reduced seed germination and thus are less likely to become invasive. Since sterile hybrids do not expend energy producing seed, they are usually very floriferous too. Garden cultivars exist at every possible plant height from 2?to 15?but wild species can be even taller. Breeders are focused on releasing dwarf selections or more tightly branched selections that can fit into smaller gardens. Some breeders are Celine Bag focusing on leaf characteristics such as leaf color, variegation, and hirsuteness.
Buddleia breeders sometimes select plants for polyploidy (more than 2 sets of chromosomes) because some polyploids are sterile. Up to 40% of the naturally occurring Buddleia species are polyploids. Buddleias have a chromosome number of n=19 (that is ?there are 19 chromosomes in each set). There are Buddleias that are natural tetraploids (4n)(e.g., Buddleia davidii), hexaploids (6n), and so on, up to 16n. Triploid Buddleias also exist and are sterile. Polyploid Buddleias tend to be less cold hardy and tend to bloom in the winter whereas diploid species tend to bloom in the summer. Asian species tend to be polyploid and new world species tend to be diploid. It is hypothesized that Buddleias are allopolyploids that arose from a intergeneric cross between Gomphostigma (2n=14) with Retzia or Nuxia (2n=24).
Five of the most prominent modern Buddleia breeders/programs Celine Box are:
Dr. Dennis Werner of North Carolina State University has a decade long Buddleia breeding program that focuses on novel leaf color, novel flower color, and dwarf habit. He makes controlled crosses of interesting individuals (including davidii, globosa, lindleyana, davidii var. nanhoensis, and fallowiana) and screens the offspring for commerically desirable traits. He is currently screening for sterility, true red flower color, and better yellows and oranges. His two recent releases lue Chip?and iss Ruby?both have won many accolades. In particular, lue Chip?is a breakthrough in Buddleia breeding for its extremely dwarf habit. In addition, it is nearly sterile and does not pose any light risk?like older cultivars. He is using lue Chip?and another dwarf hite Ball?as parents for new hybrids. He has Buddleias in the pipeline that are even smaller than lue Chip?and that are seedless. Dr. Werner has also directed graduate students in the study of genetic mechanisms of flowering in Buddleia and is experimenting with using radiation to induce mutations. This research may someday help create better flowering cultivars. In the future, look for new exciting cultivars to come out of this breeding program including a dwarf white, a dwarf lavender, and a semi-dwarf with semi-pendant inflorescences.
Dr. Jon Lindstrom of the University of Arkansas has two decade long Buddleia breeding program with a three-pronged approach. One goal is to release sterile hybrids that produce little or no seed. A second goal is to create silvery foliaged plants (like 'Lochinch') with a wide range of flower colors. His third goal is to use uncommon Buddleia species that being novel traits into garden cultivars.
Dr. Mike Dirr [retired] of the University of Georgia ran a Buddleia evaluation program that focused on attractive garden hybrids and spider mite resistance. His program released the popular hybrid cultivar Buddleia davidii ?Buddleia globosa cross called oneycomb?which is considered to be the best yellow-flowered cultivar. He also released the unique Buddleia icolor?with its two-toned flowers.
The Boskoop Agricultural Research Station in the Netherlands selected and released several pink cultivars. Elizabeth Keep of East Malling Research Station in Kent England has bred many cultivars of Buddleia with the goal of refining the habit to make bushier plants that are smaller in stature.
These folks should be commended for their wonderful work. Plant Delights Nursery is happy to offer some of their best cultivars for sale and Juniper Level Botanic Garden displays many of these fine Buddleia selections.