Do 'nativars' count as native plants?

For the purpose of supporting biodiversity in general and native insects in particular, do we have to grow only the straight species or “wild-type” of plants that grew in our region before European settlement? What about improved versions of those plants, referred to as cultivars or “nativars”? This turns out to be a complicated question.

    Unless you’re shopping at a dedicated native plant nursery, you’re likely to find few unimproved natives at the garden center. Most plants offered as natives will be cultivars that have been selected by horticulturists for desirable traits such as bigger, brighter flowers or unusual foliage color. You can spot a cultivar by a name in single quotes: for example, Echinacea purpurea ‘Sundown’ is a purple coneflower cultivar.

'Sundown' was selected for its petals' orange tint-photo Mike Peel

    Sometimes a spontaneous mutation occurs in a plant population. An observant nursery may notice the plant’s changed appearance and decide it has market value. Other cultivars are purposely created through many generations of breeding or even through genetic modification. Some are hybrids between two species. 

     Are nativars useful in pollinator gardens? It depends. Selection for horticultural use may change flower size, color, time of bloom, or foliage color. Any of these could confuse insects seeking pollen and nectar or could mean that bloom doesn’t occur when the insects need it. 

Pollinators have evolved to synchronize their life cycle with bloom times of flowers they need

Double flowers are often sterile, because in the breeding process, pollen-carrying stamens have been replaced by extra petals. These won’t offer visiting insects any reward at all.

Echinacea 'Razzmatazz' won't help pollinators

    In general, it seems that the more closely a flower resembles the straight native’s, the more popular it will be with insects. It’s an area of active research. Doug Tallamy and Emily Baisden have found that woody plants with purple, blue or red leaves are not useful to leaf-eating insects, probably because of the anthocyanins that give leaves their pleasing colors.

Heuchera 'Amethyst Mist' is pretty, but not attractive to leaf-eaters

      Annie White intensively studied pollinator visits to test gardens of native perennials and cultivars of the same species at the University of Vermont. Delaware's Mt. Cuba Center ran another perennial trial. 

Doug Tallamy and Emily Baisden vacuum up insects for study at Mt. Cuba Center

     In general, the unimproved native flowers attracted more insects, but some cultivars were also winners. A culvers root (Veronicastrum virginicum ‘Lavendelturm’ and a garden phlox (Phlox paniculata ‘Jeana’) were visited by more insects than their straight native counterparts. Researchers speculate that this is because the culvers root bloomed for longer than the straight species and the phlox had shallower flowers that made nectar easier to reach. Hybridization made flowers less useful to insects when it radically changed flower color or reduced production of pollen and nectar.

Small, shallow flowers of Phlox 'Jeana' make nectar access easy

    For gardeners who’d like to participate, three universities are running a citizen science project called Budburst that invites us to plant some flowers from a list and contribute scheduled, structured observations of their insect visitors.

    What can we take from the preliminary research? Generally straight natives seem to do the most for insects, but many nativars are useful too. We can encourage our garden centers to stock the unimproved natives. And plant breeders can help out by selecting and marketing flowers that benefit pollinators.