Bucks County Herald

Elizabeth Ludlow Bowman: Tips for the Compleat Gardener

Senna stands out in a field

Senna in a field at Bowman’s Hill.

Driving down River Road on Friday my eye was drawn by a swell of wild senna in the field at Bowman’s Hill and I decided to see it up close and get a picture so I stopped in.

All I can say is wow while thanking the senna, spellbound by the beauty in front of me, the field is resplendent in wildflowers, dark purple ironweed (Vernonia) standing out in a cluster of pinks and white swamp hibiscus (H. moscheutos) while swamp milkweeds fill the lower spaces all accented by just opening native sunflowers.

When I began to explore wild senna further, I found her overlooked by many of my favorite references. Mrs. M. Grieve has pages on senna and various medicinal uses but I am unsure if it is the same plant because the USDA informed me that the leaves are a “powerful laxative” that even grazing animals have sense to avoid.

The wild senna in this photo with a background of an amazing field is S. hebecarpa, a tall, herbaceous perennial with clusters of yellow flowers in July and August with no discernable scent, attractive to bumble and halcid bees and larval host to the sulfur butterfly.

Senna has small bladders at the bases of the compound leaves that store nectar to attract ants and ladybugs as bodyguards for its leaves, or at least that is the general thought about the feature. Senna is underused in my opinion.

I remember a stand of it along the road on the south side of New Hope. It enjoys full to part sun, loves a moist meadow but will survive drier conditions, has beautiful foliage in autumn and the long, dark, attractive seed pods pop open explosively, feeding larger game birds, quail and wild turkey.

I admit that I have never planted senna but as I see it in person (or in plant) I come to realize it is a great plant on many levels not the least of which is its height of 4 to 6 feet makes it a natural summer hedge for privacy in the yard or just a boundary of bloom. The plant has horizontal roots and a formidable tap root that keeps it upright even in wind and that feature is a huge benefit, no need to stake. Senna is a legume, a member of the pea family, and it hosts beneficial bacteria on the roots which help to make the soil fertile, alive.

This native gives to bees, ants, beetles, sulfur butterflies, wild turkeys, grouse and people so why not plant some, it is likely to be available at Bowman’s Hill Wildflower Preserve which has expanded propagation and offers more plant material.

In the Delaware Valley the rain has been abundant and some plants are really suffering because of conditions. Many gardeners have bemoaned the poor condition of hot, drought-loving perennials this season – salvias and agastache and other prairie denizens that have become regulars in many gardens.

As I have said before the Echinacea is flourishing as are the phlox paniculata, it is all a balance of wet and dry that we have no control of in seasons like this one but I prefer it to a drought.

We have had so much rain that you might notice your potted plants are looking wan, they need some food, it has all washed out and some may have died of over-watering. Make sure the pots don’t have saucers under them in all this rain unless they are seriously water-loving because an under-watered plant can be resuscitated but and over-watered one usually cannot.

Slugs and snails can be an issue for some gardeners and I have heard from people who have tried ashes, sand, beer, hand-picking and salt without success.

I used some “Escar-go” from Garden’s Alive (.com) with some success but rain every few days does not help. I heard from a reader who says she has had success with Milorganite application to deter deer.

Good to share what works.




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