A Neotropical Savanna

Back in August I saw a tree with yellow flowers, likely Senna hayesiana, growing alongside our seasonal spring. As time went by, more and more trees issued these yellow flowers so I now have easier access to them – there are a couple of trees behind our bodega (storage shed) and I can even see some yellow flowers from the kitchen window.

New individual flowers are opening daily, intriguing with their 4 fat pollen-containing stamens, curved female pistil, and 5 distinct yellow petals. [See a nice introduction to flower parts here.]

Much more is going on, as well. If you stand still near a Senna tree for some length of time, you’ll begin to hear a buzzing sound….

Senna are among the flowers said to be “buzz pollinated,” that is pollinated by insects that buzz. For example, bumblebees may vibrate the stamens leading to a specialized deposition of pollen. Well, sure enough, I did stand there long enough to watch a bee of some kind express interest in the stamens of this flower.

And then it expressed interest in the pistil of the flower.

Quite a bit of interest.

Meantime, over at another tree, a caterpillar seemed interested in the buds.

You may not be able to see in this image reduced for the web, but there are ants crawling over the stems as well. Senna has “extrafloral nectaries,” that is glands that produce nectar at the base of leaves . The ants go after this nectar and Senna thereby saves its flower nectar for its buzz pollinators.

If I raise my eyes from the caterpillar, I see some naked curved pistils (on the right in this picture).

Flower petals and stamen are gone, only the pistil remains. These pistils will eventually become seed-bearing pods, possibly quite large. If you look to the left, you’ll see some pistils that have already straightened out, on their way to becoming pods.

From bloom to pollination to seed pod production. To me it’s still magic.