Small Window: Using Natives vs Cultivars for Pollinators

Several months ago I was talking to a friend of mine from the east coast, and we were discussing pollinators and the plant lists that seem to be leaping from every corner of the web from all kinds of sources. We both agreed that the whole idea of gardening for pollinators is a good thing and that the use of natives were improving, along with understanding of native plant needs and importance. But many of the sources included or were dominated by non-natives or cultivars. Plants like:

• Buddleja davidii (Butterfly Bush)
• Foeniculum vulgare (Fennel)
• Lantana spp.
• Borago officinalis (Borage)
• Lobularia marítima (Sweet Alyssum)
• Alstroemeria (Lily of the Incas)
• Leonotis leonurus (Lion’s Tail)
• Salvia spp.
• Philadelphus lewisii (Lewis’ Mock Orange)
• Hydrangea “Anna Belle”

Red-spotted Purple Butterfly  

The list goes on with flashy plants more meant for the human eye than pollinators. It was the last species listed here that really got me thinking, though.

A couple of years ago, Connor and I thought we should compare a native species with a cultivar version of itself for pollinator use, and we happened to settle on Hydrangea arborescens and “Anna Belle” Hydrangea. We found that after a week of watching the flowers and having the staff and ourselves count species that visited the flowers that the species of different pollinators tilted heavily (5:1) to the native, straight species. We speculated that it was because of the flowers of the native are mostly fertile, having pollen, and that the cultivar having mostly (if not all) sterile flowers. We never wrote about it or defined our methods, we just kind of did it.

I got to thinking that I should try to replicate the experiment. I used the same species and in the same place that we did the first time around. I also decided to define the countable visitors as insects that interact with the flowers in a foraging manner. Not just insects that happened to be on the plant or in the area. The insect species didn’t really matter, only that they were pollinators and that they purposefully visited the flowers. I also wanted to visit the flowers and get a count at the same time every day. I watched each flower at noon every day from the 28th of June to the 10th of July for a period of 5 minutes per Hydrangea species to get the days count. I did look in many more times during the day but only to observe the type of insects to see if there was a shift during other times of day.

I did 12 counts over the 13 days (I took the 4th of July off) and ended up with a ratio of 7.5 to 2 (totals of 90 individuals for H. arborescens and 24 for “Anna Belle”)  in favor of the native. I counted 22 different species that I could discern from one another that visited the native H. arborescens and 3 species that visited the “Anna Belle”, one of which was a predator (I only know this because it was eating one of the pollinators). Many species, like the bees and butterflies only visited the native flowers!! The very small beetles, however, visited both, in part because it seems that they could wedge their way through the oversized bracts. I have a few pictures included at the end of this writing.

I know this is an anecdotal study, but I feel that it is very telling when I hear people and gardeners alike saying that there is no difference between the use of non-native species and cultivars when planting or designing or recommending pollinator gardens. There is a difference. The old excuses of natives being weedy or hard to find are no longer holding the water that they never held in the first place. Many of the species native to our area are now more widely known and can be found for sale. I hope that you find our little test illuminating and try things like this on your own. Or if you like we’d love to try it out with you, just contact us.

Good luck in your gardening and keep your pollinators happy!