“keep every cog and wheel is the first precaution of intelligent tinkering,”
~Aldo Leopold, Sand County Almanac with Essays on
Wild Ones, an organization I support, recently published it's position on nativars in the Nov/Dec 2013 issue of the Wild Ones Journal: "Due to the loss of genetic diversity and other potential problems...and because nativars are understood to be very different from native species in the wild, Wild Ones does not encourage the use of nativars. We feel this is the only position on nativars that is consistent with Wild Ones’ mission statement." (Wild Ones “promotes environmentally sound landscaping practices to preserve biodiversity through the preservation, restoration and establishment of native plant communities, ” according to it's mission statement.)A native plant species is one that occurs naturally in a particular region, ecosystem and/or habitat and was present prior to European settlement. Nurseries that sell native species grow them from seeds or divisions, without selecting a particular form of the species to the exclusion of the inherent variation found in nature.
Nativars are the result of artificial selections made by humans from the natural variation found in species so that the plants thus produced no longer reproduce naturally as straight species do through open pollination that maintains genetic diversity.
Cultivars are plants which are selected and/or bred by humans based on one or more specific traits, and then propagated in such a way that those traits are maintained. There are several different ways cultivars are created. The oldest method is selection-an individual plant naturally exhibits an atypical appearance or behavior which someone attempts to preserve by propagating that plant. In hybridization, two different species or varieties of plants are bred and their offspring is propagated. Some cultivars are naturally occurring hybrids, found in nature at the boundary between two closely related species, but many cultivars are created at nurseries by plant breeders. In genetic engineering, humans directly manipulate the DNA of plants to produce some desired trait, but due to expense genetically engineered cultivars largely to medical, industrial, and agricultural applications. Most cultivars of native ornamental plants are either selections or hybrids. A cultivar can be propagated through cloning or it can be grown from seed. Most cultivars of native plants (about 70%) are genetic clones, with exactly the same DNA, grown by cuttings, by division, or by tissue culture. Some cultivars will grow “true” to seed, which means that seedlings will have the same important trait as the parent.
Wild Ones points out that cultivars are sometimes sterile (problematic for birds searching for seed) and may have a different flower form (potentially problematic for pollinators who nay have difficulty reach the pollen and nectar). They fear there is a danger is that the nativar may interbreed with local genotype, destroying and replacing the local genotype. Or interbreeding might turn a local genotype into a plant that the local fauna can not recognize as food, or into an a variety that becomes invasive.
Wild Ones emphatically states that nativars should not be used in restorations to replicate native plant communities. While individual gardeners are free to make their own decisions when landscaping, they often find it difficult to locate native plants. Gardeners are urged to ask nurseries for straight native species plants to push growers and garden centers to begin make native plant species more readily available .
A less restrictive approach to landscaping with native plants has been recommended by many including Vincent Vizachero who manages Herring Run Nursery, a native plant nursery operated by the nonprofit watershed protection group Blue Water Baltimore. If your design permits it, and they are available, choose plants that are seed-grown from seed collected at a local wild source. If your design demands a cultivar, choose ones that are most similar in form to the local ecotype. Avoid native plant cultivars which have flowers, berries, or leaves that are markedly different from the wild variants. Avoid cultivars touted as resistant to insect damage. If pollinators are not observed on the flowers, or insect damage on the leaves, or birds eating the fruit, consider replacing the cultivar with the native species.
They counter that non-sterile nativars in the garden will cross breed with both other nativars and with the straight species. Nativars and other cultivars frequently do not “grow true” from seed set in the garden. Additionally, the best hope for saving some native species, such as the American Elm, lies in creating disease-resistant cultivars through scientific breeding programs. Some believe native plant advocates may have more success if they focus on promoting incremental changes most likely to take hold among rank and file gardeners, rather than promoting rigid guidelines in landscaping with "native" plants.