POTENTILLA FRUTICOSA TAXONOMY AND INTERNATIONAL REGISTRATION
Potentillas are commonly utilized by the landscape industry. Their hardiness, small stature, lack of major disease and insect problems, tolerance to stressful conditions, ease of asexual propagation and long season of bloom have contributed to the wide scale usage. As a consequence, there have been a large number of cultivars developed for the nursery trade. Plants have been developed throughout the world, but appear to be most popular in colder regions where the diversity of plant material is often more restricted. Until fairly recently there has been confusion about the taxonomic status of this group of plants.
The goal of this report is to provide an overview of the taxonomic research we have conducted and to review the progress we have made as an International Registration Authority (IRA) for Potentilla fruticosa. The Morden Research Centre has been recently designated as the IRA for this species and has begun to compile a database on the numerous cultivars that have been or are in the trade.
Linaeaus (1753) was one of the first taxonomists to describe the shrubby Potentilla. Since that time there have been many attempts to classify the species, or perhaps one could say group of species (see Davidson and Lenz, 1989, for details). Over time there have been at least 6 different species of the shrub described as well as over 17 different forms. Some of the more common names are presented in Table 1. This list includes 4 putative hybrids that have been used by several authors.
This plant occurs naturally over much of the north temperate regions of the world. Various taxonomic treatments have suggested the combining or the separation of species into American and European types. Plants in northern Europe are often tetraploid and dioecious whereas North American plants and those from Asia are diploid and perfect flowered (Elkington and Woodel 1963). Other reported differences between groups of plants include flower colour, plant stature, ploidy and leaf form. The reported chromosome numbers for many of the plants in question are presented in Table 1. Diploids. tetraploids as well as higher ploidy levels have been described.
The taxonomic picture becomes more clouded because of selection and introduction of cultivars. Over 160 cultivars have been mentioned in the scientific as well as popular literature (see Davidson et al., 1994, for a complete listing). Many of these are putative hybrids between different species.
DOI: 10.17660/ActaHortic.1995.413.24
https://doi.org/10.17660/ActaHortic.1995.413.24