Horsetail is a fairly bushy perennial with that have both sterile and fertile stems, the sterile stems beginning growth after the fertile stems have wilted. The sterile stems are usually much taller and bushier, with the jointed segments being around 1" long with a diameter of about 1/20th of an inch. Each segment of this unique plant contains one set of whorled, slender, erect branches each. Some stems can have as many as 20 segments and be as tall as 24". Blooming Time: Spring.