|Giant horsetails, commonly referred to the
genus Calamites, grew like bamboos and
dominated the coal-forming swamps of
the Carboniferous Period. From Smith,
Cryptogamic Botany, 1955, Fig. 151.
From the late Devonian, Carboniferous and Permian periods, some 350-300 million years ago, giant tree-like horsetails, growing up to 100 feet high, dominated early forests, sprouting from underground rhizomes, just like modern bamboos. They most likely elongated fairly rapidly, but develeped a modest amount of wood to support their large crown of branches.
Modern horsetails are for the most part fairly modest in size, living in shaded moist areas alongside the descendents of their other ancient companions, ferns and clubmosses. The largest, up to 8 ft or more in height, are found oddly in moist streamsides in dry areas of Central and South America. For an image, click on the link below, or if it is no longer active, do a simple web search for Equisetum giganteum: http://www2.fiu.edu/~chusb001/GiantEquisetum/Images/NorthernChile/LlutaRailroadScale2.html