Bees, Bugs, Blooms: Which native perennials do pollinators like best?
Pycnanthemum muticum (photo at left) is hands down best native perennial for pollinators at Penn State based on three-year trials said Connie Schmotzer, Consumer Horticulture Educator, Pennsylvania State University Extension, to the Millersville Native Plant Conference.
Four factors to keep in mind may have affected results. First, lots of pollinator plants in a small space may affect insect numbers and the flower choices insects that were present made. Second, seasonal variation in bloom time. Third, there were no trees or shrubs planted—some insect species require specific host trees or shrubs. Fourth, some plants had trouble getting established.
With those caveats, here are the top plants:
#1 Pycnanthemum muticum for the most diversity and the highest numbers. Plants flowered for 10 weeks, the longest of any in the test.
#2 Eupatoriadelphus dubius, No. 1 for butterflies, attracting 17 different types.
#3 Solidago rigida, was in the top three for pollinators for all three years. For two years it was in the top six for sheer number of insect visitors.
#4 Eupatorium hyssopifolium for the sheer number of insect visitors and pollinator diversity.
All of the plants drew pollinators, the short list of other outstanding plants include Liatris spicata, Coreopsis lanceolata, Solidago nemoralis, Asclepias incarnata, Eryngium yuccifolium (will seed in), Coreopsis rosea, Penstemom calycosus and Monarda punctata (tolerates dry soil).
On cultivars (a.k.a. nativars) vs. straight species? Some cultivars attracted greater pollinators than the straight species, some attracted fewer, she said.
It’s difficult to figure out where some cultivars come. “Is it a sport? A plant someone found? Or manmade?” Eupatorium maculatum vs. Bartered Bride, for instance. Bartered Bride attracted significantly more bees and syrphid flies, but not butterflies. But with Monarda fistulosa vs. Claire Grace, the straight species was the clear winner. “We know what the results show us, but not why.”
The worst plant for attracting pollinators: Symphyotrichum novae-angliae Purple Dome.
A pdf handout summarizing trial results is available here:
NewTerrain newsletter August 25, 2015.