Wednesday, July 27, 2011

Wild Senna

I really enjoy seeing attractive native plants increase their numbers. Wild Senna, Senna marilandica, was very uncommon at Blue Jay Barrens when I first began managing this property. Each year I find new locations for this plant. It’s now becoming common in the former crop fields.

This lovely plant easily reaches a height of five feet. I think of it as the monster version of its close relative the Partridge Pea. Compound leaves radiate from a central stalk and give the plant an almost shrubby appearance.

The leaves show a sensitivity to disturbance and respond by closing the leaflets when roughly handled. As a child, I was always fascinated by the ability of plants to make rapid movements such as this. My favorite was the common houseplant known as the Sensitive Plant. I remember being in trouble on several occasions when my mother took me along on visits to the neighbors and I prodded their Sensitive Plants until every leaflet was tightly closed.

At the base of each petiole there is a small nectar producing gland. Ants usually stake out these positions and harvest the nectar. The plants probably receive some protection from predation by having the ants present.

Of course, the plant serves as a home and food source for many insects and other small animals. Whenever I see a bee oddly positioned on a flower, I assume that it is being eaten by something. At this time of year, yellow flowers usually mean yellow crab spiders.

I think one measure of a plant’s worth is the number of different animal species it’s able to support. The sight of an unblemished plant makes me wonder why it’s not being eaten. I was recently being given a garden tour by someone who prides herself on using native plantings in the landscape. As I bent down to view a larva busily chewing a leaf, she reached out, picked the leaf, threw it on her sidewalk, mashed it with her foot and then thanked me for calling the offending creature to her attention. I usually don’t offer my opinion unless asked, but once asked, I’ll divulge all of my thoughts without trying to be diplomatic. My face must have had a look of disapproval, because she asked me what was wrong with stomping that worm. I tried to explain to her the miracle of a random collection of native plants transforming into a functional ecosystem with native animals living and cycling along with the plants. I don’t think I convinced her and I think she was perturbed by my referring to her carefully planned planting beds as a “random collection of native plants”. Anyway, the tour ended shortly after the stomping incident.

The more you look, the more insects you find. At first glance I thought this was an Assassin Bug nymph and wondered if the approaching beetle might be in danger. A closer look makes be think it’s actually a Spiny Plant Bug. Instead of a beetle predator, it’s more of a competitor. It would be nice to just sit and watch these insects go about their normal business, but it seems that as soon as I get close enough to see what’s going on, the insects detect my presence and begin moving towards cover.

1 comment:

  1. Fascinating about the insects. The flower itself is so pretty. Viewed independently, without considering size and leaves, it reminds me a little of an orchid a friend grew while we were on board a ship together. He went home on vacation while we were still on board and he asked me to care for it while he was gone for a few weeks. All went well and the plant was happy and well when he returned. He called it "Dancing Lady Orchid." So pretty.