Wildflower Wednesday: Wild Senna

 Senna marilandica, Senna hebecarpa

Let me be absolutely honest with you from the start. I have no idea if my plants are Senna hebecarpa or Senna marilandica. For many of us they're indistinguishable from one another until their seeds ripen. The pods look the same, but they behave differently, Senna hebecarpa seeds will be expelled from their pods, while the seeds of Senna marilandica will stay tightly enclosed within the seed pod for months. I'll come back and relabel this post as soon as I know which Senna I have.

In the meantime, our Wildflower Wednesday star will be known as Wild Senna, the beautiful.

Wild Senna is a perfect plant for any gardener who loves pollinators, especially lovers of the bumbles. It seems that bumbles are picky eaters and prefer plants with nutrient-rich pollen. Wild Senna is one of their preferred pollen sources.

How do I know this?

 A "2016 study by researchers at Penn State found that bumble bees preferentially visit flowers that produce pollen that has higher protein-to-lipid ratios, and wild senna was the favorite of bumble bees amongst the plants used in the study." In case you're curious,
spiderwort and Culver's root were also among the highest visited plants in the study.

Wild senna is a member of the Fabaceae/pea family and native to eastern North America. Long lived and tall (could be 7 foot) it prefers sun/part sun and uniformly moist soil to thrive. Our star has flowers that are unusual for a member of the Pea family. Rather than curling to form the banner, wings and keel that are common Pea family characteristics,Wild Senna’s petals are open and distinct. It does have other characteristics that make it standout as a Fabaceae family member: pea like pods and compound leaves.

Source

Bumblebees and sweat bees are favorite visitors, although, bumbles are the primary pollinators for Wild Senna. Bumbles visit for the aforementioned nutrient rich pollen. The collected pollen feeds the growing larvae and provides provision for the long winter.

Like Partridge peas, Wild Senna does not produce nectar in their flowers, instead, the 'nectar' is found in little bulbous growths at the base of each stem called an 'extrafloral nectary'. These nectaries attract ants, flies, wasps and beetles. Occasionally, butterfly visit them. So far, I've only seen these large ants and a few smaller ones. I've seen seen Cloudless Sulphur butterfly flitting about the garden, but, I've not seen them on the Wild Senna. Which surprises me, since Wild Senna is a host plant for their cats.

It's a great plant with excellent wildlife value. 

There's only one problem with Wild Senna! It doesn't bloom nearly as long as I want it to! But it does have height, good looking compound leaves and blooms exactly when Bumbles need the pollen the most....Late summer when many are provisioning their nests for winter (especially in gardens further north of me).

aren't the seed pods cool

The flowers give way to pendant, pea-like seed pods which turn black in fall and are either expelled (if S hebecarpa) or persist (S marilandica) on the plants after the plant has died back to the ground in late fall.

I think the plant in seed is a beautiful as in flower.

This is a plant that belongs in every garden, especially pollinator gardens. I've only seen it offered online (most often as seeds). It's frustrating to see the same old same old perennials at nurseries when there are fantastic native plants that make the most sense for our gardens...but, I digress.

source

I've been imagining it as a replacement for the notorious Forsythia  Hedge (slowly removing). I can see it now, Wild Senna with it's beautiful compound leaves and stellar butter yellow flowers with Panicums, Indian Grass, Verbesinas, New York Ironweed, Joe pye weed, Boneset, and the ex-Asters. Note that all those plants prefer moist soil, which I don't have, but, oh doesn't that sound like a beautiful garden bed? 

This fall, I will sow seeds near the ex-asters and the Texas Star Hibiscus (they're located on a soaker hose route). I think they will dance well together. What do you think of planting  Packera aurea at it's feet for spring color?

Which ever Senna this turns out to be, it's so very welcome in my garden.
xoxogail


The Particulars

Family: Fabaceae
Common Name: Wild senna
Botanical Name: Senna hebecarpa or Senna marilandica
Distribution: Senna hebecarpa is native across the Northeastern U.S. from the Great Lakes as far south as Georgia. Senna marilandica has a broader range extending further west and south. It is generally found on disturbed sites, moist meadows, pastures, fields or roadsides in full or partial sun. It often flourishes within the floodplain of rivers. While it prefers moist soils it will also grow on dry sites.
Light Requirements: Full Sun, Half Sun/Half Shade
Soil: tolerating wet and dryer soils (once established) 
Flower: Small butter-­‐yellow flowers that grow in a profusion at the top of the stems.
Height: 3 to 7 foot tall
Bloom Time: July and August in middle Tennessee, I hope into the fall
Fruit: Senna marilandica~pendant, pea-like seed pods (to 4" long) which turn black in fall and persist on the plants well after the plant has in the normal course died back to the ground. Senna hebecarpa The dark brown seedpods are about 10 centimeters long when fully mature in September – October. The seed pods have 10 – 18 segments and split explosively when ripe.
Host Plant: Cloudless Sulphur, Sleepy Orange, and Little Yellow, Ceraunus Blue and Gray Hairstreak  caterpillars. A good nectar source that also attracts many pollinators in addition to butterflies. 
Companion planting:  Switch Grass, Indian Grass, wingstem, New York Ironweed, Joe pye weed, Boneset, Asters. To be sure you have good color in the Spring you can use golden Groundsel which flowers in late May into June. Wild Senna is an excellent plant for a wet meadow planting or garden border. Put it in the middle or rear of the bed. Range: Senna hebecarpa is native across the Northeastern U.S. from the Great Lakes as far south as Georgia. Senna marilandica has a broader range extending further west and south.
Comments: Is not grazed by mammals.

****I declare that our wildflower star star is Senna marilandica!****

 The seed pods are the giveaway to me!
 
Welcome to Clay and Limestone's Wildflower Wednesday celebration. WW is about sharing and celebrating wildflowers from all over this great big, beautiful world. Join us on the fourth Wednesday of each month. Remember, it doesn't matter if they are in bloom or not; and, it doesn't matter if we all share the same plants. It's all about celebrating wildflowers. Please leave a comment when you add your url to Mr Linky.




Gail Eichelberger is a gardener and therapist in Middle Tennessee. She loves wildflowers and native plants and thoroughly enjoys writing about the ones she grows at Clay and Limestone. She reminds all that the words and images are the property of the author and cannot be used without written permission.