Dracocephalum 

Dracocephalum is a genus which contains some 50 species of annuals, perennials and evergreen subshrubs. The species are found in a variety of habitats that range from rocky and grassy slopes to dry woodland areas predominately in Eurasia. There are however a few types that can be found in N. Africa and in the northern part of the United States. In general their features include square stems which are typical of species in the Lamiaceae / Labiatae family, two lipped flowers on whorls of terminal or axillary racemes, opposite arranged leaves which are aromatic, toothed to entire, and lobed or pinnatisect.

Cultivation generally requires a well drained relatively dry soil and exposure to full sun with some midday shade. There are a few species which are not tolerant of winter dampness and require protection during that period.

Propagation is by seed in early spring or in containers in cold frame in autumn. They may also be divided in autumn and placed in cold frames to overwinter. Cuttings should be rooted and planted during the mid-spring season.

These species are occasionally affected by rust, mildew, southern blight, and spider mites. Despite these few susceptibilities which are easily controlled by natural or chemical controls, they serve well in mixed borders, rock gardens, and herb gardens. (1)

The following is a brief description of some of the varieties of Dracocephalum.  Following the descriptions are pictures of not only those described but many additional varieties as well.

Northern Dragonhead (Dracocephalum ruyschiana) is a perennial found in open woods or dry grassland. It has blue and violet (and occasionally white) flowers.

Dracocephalum (Dracocephalum thymifolium) is an annual, usually growing in bare or waste places. It has lilac blue flowers.

Dracocephalum parviflorum.  It's common names include: American dragonhead, false dragonhead, dragonhead, dragon's head. American Dragonhead is a bushy plant with hairy, square stems, opposite leaves, and inconspicuous flowers borne in spikes. The flowers have spiny-tipped, scale-like leaves called bracts surrounding them.  American Dragonhead can grow as an annual or a biennial. It reproduces from seed.  Note:  this plant is listed as a noxious weed in many areas.

Dracocephalum grandiflorum:  A perennial native to Western China.  This species makes attractive clumps with crowns of large, nearly heart-shaped, deep green leaves with scalloped margins. From these emerge 6-12" stems which carry dense whorled clusters of two-lipped flowers, hooded above, each up to 2" long. The flowers are vivid blue-violet in color.

Dracocephalum rupestre:  A perennial native to Siberia.  It's common name is Dragon's Head.  It has attractive foliage and flowers in summer. The blooms are hooded, two inch flowers of an intense deep blue color.  It grows to a height of 8" and requires full sun to light shade.

http://word.sytes.net/

http://www.polenth.demon.co.uk/other/typeplant.html

(1) http://botanicalresources.1hwy.com/Dracocephalum.html (nearly all the pictures were taken from this site as well)

(2) Some photos are originally from: http://www.hkr.hel.fi/viher/natur/Dracocephalum_moldavicum.shtml