I have always been a fan of nature documentaries. One particularly captivating scene is that of the savanna watering hole. Here, predator and prey line up side-by-side, congregated at the source of one of southeastern Africa's rarest summer resources: water.
Modern cities are equally limiting for most insects--vast expanses of concrete, buildings, mowed turf grass, and occasional ornamental plants in a sea of mulch. It comes as no surprise that the oases of native habitat gardens can be densely populated with diverse insects delighting in the rewards of pollen, nectar, and edible leaves (leaves the herbivorous insects evolved to eat, unlike those of exotic undigestible plants). Even a single flower can seem akin to the savanna watering hole, with dozens of unique species basking in the abundant resources.
In late summer, one of my favorite suburban oases plants is wild golden glow, or Rudbeckia laciniata. Unlike black-eyed susans (what people often think of when they hear Rudbeckia), Rudbeckia laciniata is a stout plant, reaching upwards of 8 feet tall and wide in ideal conditions. It is often found along woodland edges or stream banks in the wild, but I found found it rather adaptable when planted. It works quite nicely as a backdrop to a garden bed against our deck, where the towering flowers can reach over the deck railing--the perfect height for observing visitors.
On a cloudy day in mid-August, in our Omaha, Nebraska yard, I had the pleasure of observing a handful of bee species across several families, unique flies, wasps, and beetles. All on a single flower.
The tiny metallic Ceratina sp. (family Apidae) carpenter bees gather pollen on their legs before returning to their nests inside last year's flower stems. The equally small Megachile sp. bees might look similar to the untrained observer, but can be easily distinguished by their preferred location of pollen storage--the underside of their abdomen.
Next, the larger Melissodes sp. bees can be distinguished by their longer antennae and furry leg chaps (reminiscent of Ugg boots). I often observe this genera of bees, and their relatives, on yellow flowers of the composite family (Asteraceae) such as Rudbeckia sp., Silphium sp., and Helianthus. In fact, some are known specialists to these flowers.
I watched Halitctus ligatus, a generalist eusocial bee, arrive to the same flower that had been visited by several other just minutes before. After seeing each bee so loaded with pollen, could there be anything left for the new arrival? Apparently so, as the Halictus' pollen load seemed to noticeably grow as it spent several minutes on the single flower before hopping to the next.
Much like the watering hole, I found myself wondering if these bees appreciated how rare this plant is in the area. I haven't surveyed the neighborhood exhaustively, but I could be almost certain that this garden has the only Rudbeckia laciniata within the flight range of these smaller bees. Although wild golden glow is certainly not a rare species, nearly all native plant species are locally rare within our cities. Planting a small native garden in the corner of a public park, a backyard, or at a school could increase the resource value of the area exponentially. Of course, these plantings do not have to be altruistic. These plants bring incredible joy into the spaces where humans live, by bringing in all sorts of diverse lifeforms. Instead of watching the animals gather at the watering hole through the television, we can have our very own oasis within walking distance from our homes, with something new to see every day.