Variegated Horsetail

Equisetum variegatum 
 
 
 
Horsetails are an ancient and primitive plant family related to ferns. An unusual plant with dark, evergreen erect stems with furrowed ridges. Tolerant of acidic soil. Would provide an unusual and striking texture along a pond or water feature where water is seeping.  Spreads primarily vegetatively and also by spores in mid summer.