Yellow, yellow flowers everywhere. Walking a familiar part of the trail, my eyes scan the usual floral sights of late July: the Silphium brothers Cup Plant (big brother) and Rosinweed (little brother); inspecting the Gray-headed Coneflowers for Camouflaged Loopers...hello, what's this?
My brain, seeing the shape and color of the bushy yellow inflorescence, quickly said "Showy Goldenrod, nothing unusual, move along" followed immediately by "isn't it a little early for goldenrod?" and directing the eyes back for a closer look.
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| Bees and ants visiting senna flowers. |
Despite the initial vague resemblance...definitely not a goldenrod. For one thing, the leaves are compound, with tidy paired leaflets. And the yellow flowers comprising the showy inflorescence were big and blowsy, with many dark anthers projecting from the loosely open petals. A senna! Has that been there all these years and I've just never noticed it before now? It's hardly a subtle plant.
There are two similar species of senna in our area, which can be tricky to tell apart: Maryland Senna (Senna marilandica) and American or Wild Senna (Senna hebecarpa). Some points mentioned to help identify are the hairiness of the style (longer on Wild Senna) and the behavior of the seedpods. (I am not confident in our senna here so I will just call it a senna.)
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| Knob-like nectaries are situated at the base of leaves. |
They are members of the legume family and are native to the eastern U.S., with Maryland Senna having a slightly wider range, reaching Nebraska and points south. All those stamens (ten in total) provide pollen to bumble bees (and many other pollinators).
If you look closely at the base of the leaves, you'll find a curious rounded knob: an extrafloral nectary, which makes sweet nectar available to ants, wasps, ladybird beetles, and other insects that may take advantage of the nourishment, possibly providing protective services to the plant in exchange. (Another yellow-flowered native legume, Partridge Pea, similarly provides nectar in the form of little pots at the base of the leaves.)
It's a beautiful plant, and provides a lot of interest not only to wildlife but human observers too. I'll definitely be keeping an eye out for it in the future.
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| Really...not very subtle. |
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