|About 200 species|
The genus is traditionally placed at family rank with the waterleafs ( Hydrophyllaceae) in the order Boraginales. The Angiosperm Phylogeny Group, recognizing that the traditional Boraginaceae and Hydrophyllaceae are paraphyletic with respect to each other, merges the latter into the former and considers the family basal in the Euasterids I clade. Other botanists  continue to recognize the Hydrophyllaceae and Boraginales, but to make them monophyletic move the present genus to the Boraginaceae.
As with many[ weasel words] species in the Boraginaceae, contact with the hairs of some species of Phacelia can cause a very unpleasant rash[ citation needed] similar to that from poison oak and poison ivy in sensitive individuals. The major contact allergen of Phacelia crenulata has been identified as geranyl hydroquinone. The similar-appearing species Eriodictyon parryi (poodle-dog bush), a common chaparral plant of Southern California, is also a frequent cause of skin irritation.[ citation needed]
- Gilbert et al. (2005)
- E.g. Gottschling et al. (2001)
- Gilbert, C.; Dempcy, J.; Ganong, C.; Patterson, R.; Spicer, G.S. (2005): Phylogenetic Relationships within Phacelia subgenus Phacelia (Hydrophyllaceae) Inferred From Nuclear rDNA ITS Sequence Data. Systematic Botany 30(3): 627-634.
- Gottschling, M.; Hilger, H.H.; Wolf, M. & Diane, N. (2001): Secondary structure of the ITS1 transcript and its application in a reconstruction of the phylogeny of Boraginales. Plant Biology 3: 629–636.
- Olmstead, R.G.; Kim, K-J.; Jansen, R.K. & Wagstaff, S.J. (2000): The phylogeny of the Asteridae sensu lato based on chloroplast ndhF gene sequences. Mol. Phylogenet. Evol. 16: 96–112.
|Wikimedia Commons has media related to Phacelia.|
- Panorama of a Phacelia Field (QuickTime required)