The growing interest in gardening with native plants for environmental benefit has led to confusion over what constitutes a native species. Gardeners often encounter plants labeled as native that possess unusually vibrant colors, compact sizes, or unique leaf patterns. This raises questions about their origin and ecological value. Understanding the distinction between a wild native plant and one cultivated by humans is necessary for making informed decisions for any landscape project.
Establishing the Core Definitions
A plant considered a native species, often called a “straight species,” occurs naturally in a specific region, ecosystem, or habitat without human intervention. These plants have evolved over thousands of years within their local environment, adapting to the specific climate, soil conditions, and pests. Because they reproduce through open-pollinated seeds, native plant populations maintain a high degree of genetic diversity, which is a major factor in their resilience to disease and environmental changes.
In contrast, a cultivar is a plant selected and propagated by people for a specific desirable trait. This includes plants chosen for characteristics like different flower color, a more compact growth habit, or increased disease resistance. To ensure the selected trait is preserved, cultivars are typically propagated asexually through cloning, such as taking cuttings. This results in every plant being genetically identical to the parent, meaning that while a cultivar may have originated from a native plant, it lacks the genetic variability of the wild population.
The Role of Human Selection in Classification
Cultivars are generally not considered native plants because the act of human selection and cloning fundamentally alters their status from a wild population. The core principle of a native species is that its traits and genetic makeup are the result of natural selection in a specific location. Once a plant is singled out and artificially propagated for a specific human-chosen characteristic, it becomes a cultivated variety, regardless of its parentage.
This classification distinction led to the common use of the term “nativar.” Nativars are cultivars derived from a native species, meaning they have a native lineage but have been manipulated for horticultural purposes. While the scientific classification often remains the same as the straight species, the selected traits and clonal propagation disqualify the plant from being classified as a true, wild native species.
Evaluating Ecological Performance
The most significant difference between a straight native species and a nativar lies in their ecological performance and function within the local food web. Studies have shown that nativars with highly modified traits, such as “double flowers,” can severely reduce or eliminate resources for native insects. Double-flowered varieties, for instance, often have their reproductive organs converted into extra petals, which can block pollinators from accessing nectar and pollen or result in a sterile flower with no floral reward.
Cultivars selected for altered leaf color, specifically those with red or purple foliage, have been shown to be consistently less palatable to native insect larvae, like caterpillars, compared to their green counterparts. This is because the pigments that create these colors, known as anthocyanins, can act as feeding deterrents for insects that rely on the leaves for food. Since caterpillars are a fundamental food source for nesting birds, this seemingly minor aesthetic change can reduce the plant’s capacity to support the local ecosystem.
Furthermore, the loss of genetic diversity in clonal nativars poses a long-term risk to ecosystem resilience. Straight species maintain diverse genetics, allowing the population to adapt to new diseases, pests, and the increasing variability of climate change. By contrast, landscapes dominated by genetically identical nativars face a heightened vulnerability, as a single pathogen or stressor could potentially wipe out all individuals of that cultivar. Some nativars with minimal modification, such as those selected for disease resistance, may be comparable to the straight species in pollinator attraction, but others prove inferior, underscoring the need to evaluate each cultivar individually.
Choosing the Right Plant for Your Landscape
When choosing plants, the decision between a straight native species and a nativar should be guided by the primary goal for the landscape. For projects focused on habitat restoration, maximizing biodiversity, or supporting specialized native insects, the straight native species, ideally a local ecotype, is the most beneficial choice. These plants guarantee the necessary co-evolutionary resources, such as specific leaf chemistry for larval feeding, are present.
Nativars can be useful additions when specific aesthetic or functional requirements are needed for a small garden space. For example, a compact cultivar may be necessary for a restricted area, or a sterile variety may be desired to prevent unwanted self-seeding. In these cases, it is advisable to select cultivars that have been minimally modified. Gardeners should avoid those with traits known to negatively affect wildlife, such as double flowers or deep purple foliage.