When I researched the plant I found some very interesting facts. They are old--very old. They go back in the fossil record over 150 million years to the Paleozoic era, when little trilobites like this one were swimming around this part of the globe. The ancestors of our modern horsetails dominated the understory of the forests during that time. They are also pretty unusual in the way they reproduce via spores rather than seeds.
Up until now I have painted them with the warm golds more representative of the end of the growing season. This example is a detailed portion of a newly completed piece which shows the horsetails in their growing phase.