Subalpine.  Woodlands, meadows, wetlands.  Summer.
Upper Calico Trail, July 21, 2005.

Monkshood often is mistaken for its cousin Delphinium barbeyi; the two grow in similar moist habitats and both have broad, leafy, sometimes shrub-like bases, and very tall flower stalks.  Delphinium, though, reaches seven feet and Monkshood only five.  Monkshood flowers are most often intensely deep purple with a high arching hood.  Delphinium flowers range from inky blue through violet to purple and have a distinctive spur.  Delphinium is far more common but a discerning eye will often find Monkshood growing with Delphinium. The pictured plants are just over two feet tall and will grow another foot or two.   Notice the characteristic deeply incised leaves of Monkshood. 

"Aconitum" is the classical Latin name and probably means "unconquerable poison", referring to the plant's toxicity.  "Columbianum" refers to the plant's American (Columbian) location.

Subalpine.  Woodlands, meadows, wetlands.  Summer.
Sharkstooth Trail, July 30, 2004.

Subalpine.  Woodlands, meadows, wetlands.  Summer.
Pass Creek Trail, Engineer Mountain, August 2, 2005.

This is a typical setting for Aconitum columbianum, buried in other plants that also enjoy wet roots; only Aconitum columbianum's deep purple flowers poke through.  The Corn-like leaves are those of Veratrum tenuipetalum, and the yellow Sunflower is Senecio triangularis.

Delphinium

Leaves of Monkshood, Geranium richardsonii, and Delphinium barbeyi are quite similar.