Native species vs nativars: the real debate
"Nativars" -- cultivated varieties (cultivars) of native plant species -- have become a central controversy in ecologically minded gardening circles. The debate is straightforward in principle: when you buy 'Black Lace' elderberry (*Sambucus nigra* 'Black Lace') instead of the straight-species.
"Nativars" — cultivated varieties (cultivars) of native plant species — have become a central controversy in ecologically minded gardening circles. The debate is straightforward in principle: when you buy 'Black Lace' elderberry (Sambucus nigra 'Black Lace') instead of the straight-species native Sambucus canadensis, does it provide the same ecological value to native wildlife? The answer, increasingly, is: it depends on which trait was changed.
Per Xerces Society research, changes in flower color, flower structure, and foliage color — all common in cultivar selection — can significantly affect the ability of native insects to use those plants.
What the research actually says
Riedel et al., 2016 (Native Plants Journal)
Per research cited by Xerces Society, Riedel et al. (2016) compared insect visitation to straight-species coneflower (Echinacea purpurea) and several nativars with altered flower color and structure. Native bees visited straight-species plants at higher rates than double-flowered nativars. Single-flowered cultivars with similar flower architecture showed comparable or only slightly reduced visitation.
Key finding: Double-flowered forms (where petals replace reproductive structures) and forms with dramatically altered flower color reduce pollinator access significantly.
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PennState Extension nativar research
Per Penn State Extension, entomologists at Penn State compared straight Echinacea purpurea, several nativar selections, and non-native controls for bee diversity and visitation rates. Results showed:
- Straight-species plants attracted significantly more native bee species than most nativars
- Some nativars with minimally altered flower color attracted similar bee diversities to the straight species
- Double-flowered and non-typical-color nativars attracted substantially fewer native bees
Tallamy's caterpillar data
Dr. Douglas Tallamy (University of Delaware) has studied the host plant use of Lepidoptera (caterpillar-producing moths and butterflies) on native plants and nativars. Per Xerces Society summarizing his work, dark-foliaged nativars of native plants (like dark-leaf elderberry, dark-leaf coneflower) may reduce caterpillar feeding. Caterpillars rely on plant chemistry (secondary metabolites), and cultivar selection often changes those metabolites alongside the visible traits.
This is a hypothesis with supporting data, not a closed conclusion. The degree of change varies by species and cultivar.