Black-eyed Susans are easy to grow and will attract many pollinators to your garden. The dark center or eye of the flower head holds 250 to 500 individual flowers, and to pollinators, each one of these is a shallow nectar cup. These are shallow enough that even small wasps and flies can drink from them, and many small wasps and flies are predators or parasitoids of pest insects. These tiny, dark flowers bloom from the outer rim of the eye and progress inwards with time. It’s a buffet that attracts a wide variety of small to medium-sized pollinators, including many species of insects beneficial for pest control. This blog provides a few examples of the wonderful insects you can attract to the home garden by planting Black-eyed Susans.
A Black-eyed Susan isn’t a single flower, it’s actually hundreds. Notice the individual corollas of the “eye”, and the yellow pollen along the outer ring which indicates those flowers are in bloom. Watch a pollinator visit, and you’ll notice that they rotate around, drinking nectar from each one of the tiny blooms in this ring. The Metallic Green Bee, shown here, is a good example of the small bees that enjoy Black-eyed Susan’s big, soft, landing pad and shallow flowers. Notice the pollen packed onto the bee’s hind legs.
Black-eyed Susans have a hidden superpower that draws in the bees. Can you see it? Notice how the subtle darkening toward the base of the yellow petals forms a bulls-eye circle around the disk. That darkening is actually caused by an ultraviolet pigment which bees can see much better than we do, and it forms a strong visual cue that leads them to the nectar and pollen at the flower’s center. The insect in this photo, however, is not a bee. Did you think it was? The strong black and gold color pattern is a deception! This is actually the Transverse Flower Fly, a type of Syrphid Fly, and a particularly common visitor on Black-eyed Susan. Syrphid Fly adults drink nectar, but their larvae are predators and help to control many pest insects such as aphids and whiteflies.
Wasps aren’t known for being effective pollinators, but the Scolid Wasps are an exception. Look at all the pollen on this one! I can’t find a common name for this wasp, but it is in the genus of Flower Wasps, and given the scientific name, I propose we call it the Noble Flower Wasp. In late summer you may see large numbers of these wasps flying low over a lawn. They are hunting the Japanese Beetle grubs that terrorize your lawn, so they are very beneficial insects indeed!
By Sara Tangren, Ph. D., Sr. Agent Associate, Sustainable Horticulture and Native Plants, and Christa Carignan, Coordinator, University of Maryland Extension, Home & Garden Information Center