Plant Story Phacelia hastata, Silverleaf Phacelia

This rather odd-looking flower was common in the pine forest at 9000' in the Rocky Mountains in late June.  

silverleaf phacelia, Phacelia hastata

It is silverleaf phacelia, Phacelia hastata, in the waterleaf family, Hydrophyllaceae. 

The genus Phacelia has 210 species, all native to the Americas, 167 of those are native to North America, only. They are found all across the continent, particularly in dry locations, but most species have a range of only one or two states. Silverleaf phacelia is an exception, being found from the Rocky Mountains west to the Pacific. It is one of only a couple widespread species. Also widespread in the West is varied-leaf phacelia, Phacelia heterophylla, with a similar range. Silverleaf has linear leaves with prominent veins and a cluster of rather big pale flowers with the stigmas and stamens protruding. Varied-leaf has at least some leaves divided as well as linear, and the flowers, smaller than silverleaf's, are in tightly coiled cluster. 

silverleaf phacelia Phacelia hastata 

The plant is quite hairy, giving it a silvery look, though you don't see it in my photos. When dry, those hairs can be quite irritating, as people who have tried to collect seeds will attest.  

Studies in Utah and Nevada found bumblebees, 12 different genera of native bees, and a pollen-collecting wasp (Pseudomasaris) visiting the flowers and pollinating. Pollination observations in the mountains of Colorado observed constant and continuous bumblebee activity on the plants. The pollen of a single flower will pollinate that same flower, creating a seed (self-compatible), but the shape of the flower prevents it from getting there unless the pollen is brushed onto an insect and brushed off again onto the flower's stigma, so pollinators are required for seed production. 

The seeds are about 1/16" (under 0.1") long, and attractive food for small mammals, like ground squirrels, birds like sage-grouse, and a variety of insects. The hairy leaves are reportedly not much eaten by grazing mammals, but the top of the left stem in the plant below was clearly chopped off, probably by an elk, so animals at least try them. 

silverleaf phacelia, top of left stem severed by
a browsing animal

Silverleaf phacelia is a hardy plant that grows well in harsh, open sites, so is used a lot revegetating places in the West. Below is the sort of habitat where I see it, but it also grows in really open sites.

silverleaf phacelia habitat on the eastern edge of its
range (low elevation eastern slope of Rocky Mountains)

The scientific name that is often used as the common name, Phacelia, is based on the Greek word phakelos, bundled, for the clustered flowers. The species epithet hastata is a Latin word meaning "spear-shaped" and refers to the leaves. Other members of the genus Phacelia are called scorpionweeds. All the members of the genus have a curve to the flower stalk, but it is subtle in silverleaf phacelia, while the flowerheads of other Phacelia species are clearly shaped like a scorpion's tail. Some of my older books call Phacelia hastata spear-shaped phacelia, making a common name out of the scientific name. 

silverleaf phacelia Phacelia hastata

Phacelias can remind you of borage family plants, which are also hairy and have curved flower stalks.  Expert opinion has varied, creating the Hydrophyllaceae, the waterleaf family, with Phacelia, Hydrophyllum (waterleaf) and 8 other genera, 250 species total, all New World (see Hydrophyllaceae on the Angiosperm Phylogeny website link) as a separate family. But then it was merged into the borage family, Boraginaceae, which is a worldwide group with another 94 genera, containing 1,793 species. Even more recently, Hydrophyllaceae was separated out of the Boragninaceae again. As of this writing, the Angiosperm Phylogeny website, at the Missouri Botanic Garden in St. Louis, recognizes the Hydrophylllaceae, but if you look it up on WFO, World Flora Online, out of Kew Gardens in England, they place Phacelia and the Hydrophyllaceae in the Boraginaceae (link). When experts don't agree, as in this case, the rest of us can use whichever family we prefer. 

There was a time when botanists arranged their regional plant id books (floras) by the relationships between the families, so Hydrophyllaceae and Boraginaceae would be next to each other and you could easily look for the plant you found in several related families. But plant classification has been so much revised that people gave that up and are now mostly organizing their books alphabetically by family. In most cases, if it looks fuzzy and curved, you will have to check to see if the book recognizes Hydrophyllaceae or just Boraginaceae. (Mind you, organizing by relationships meant that you had to use the index to find most families in the book, now that ir is alphabetically by famiy it is easy to go to a particular family; each system has flaws.) In a popular wildflower book organized by flower color, check white, cream, and purple looking for silverleaf phacelia. 

a borage, genus Borago, showing the characteristic
scorpion curl. You have to get closer to see how
hairy it is.

Silver-leaf phacelia is a shapely plant with pretty flowers that is very attractive to bees. It easily noticed when flowering and inconspicuous otherwise. 

Comments and corrections welcomed.

References

Ackerfield, J. 2022. Flora of Colorado. 2nd ed. Denver Botanic Gardens. BRIT Press, Fort Worth, Texas.

Gucker, G.L, and N. L. Shaw 2021. Silverleaf Phacelia. Phacelia hastata Douglas ex Lehm. Hydrophyllaceae. Waterleaf Family.Western Forbs: Biology, Ecology and Use in Restoration. BLM.Gov link

Kathy Keeler

A Wandering Botanist

More at awanderingbotanist.com

Join me on Facebook: https://www.facebook.com/AWanderingBotanist