Horsetails are an ancient order of vascular, spore-forming plants -- being the oldest members of the Pteridophyta (Ferns and their allies). They are the long distant relative of the large tree-like plants that grew during the Carboniferous period nearly three hundred million years ago.
In the early spring, the fertile stems of horsetails break through the leaf litter. At the top of each fertile stem is a solitary "cone" or strobilus that is covered with hexagonal scales. The undersides of the scales hold the spore producing sporangiophores.
When the strobilus matures, the scales expands, releasing the spores to be spread by gentle breezes.
The green infertile stems begin breaking through the leaf litter shortly there after.
