E. douglasii - very similar to E. sphaerocephalum sublineare. ID notes at https://www.inaturalist.org/observations/160463297
E. elatum - late flowering, large ovate to arrowhead shaped basal leaves on petioles about leaf-length, very tall flower stems, usually highly branched, leafless, giving a rather sparse open look with small flowers.
E. heracleoides - widespread, larger and shaggier than sphaerocephalum with more open flower umbels and usually with large leafy mid-stem bract (often missing in certain areas of central WA), largish plant, flowers cream to pink infused. https://www.inaturalist.org/observations/165614783
E. niveum - low sprawling shrub when not in flower, with ovate to broadly lanceolate leaves on long petioles, densely wooly and usually held vertically. Late flowering freely branched sprays of small flowers, usually white often with narrow pink stripes. Leafy bract at each flower stem branching. Flower stems persist through the winter and are often dark reddish brown. Inner whorl petals (tepals) narrower than outer petals (dimorphic tepals, same as E. strictum). https://www.inaturalist.org/observations/131109378 and https://www.inaturalist.org/observations/160462358
E. ovalifolium - very low silvery to greyish foliage (occasionally green) varying from small upright paddle-like leaves to densely packed curled leaves, often forming sizeable mats. One variety has brown margins on leaves. With close inspection three tepals are much narrower and longer than others (dimorphic tepals). Flowers can be candy-striped, or pale to bright yellow, or sometimes dark pink or even red. Flower bracts form a cluster of several conical bract sheaths, each bearing several flowers. https://www.inaturalist.org/observations/171453389
E. sphaerocephalum - up to 40 cm (16 in) tall, intermediate growth form between thymoides/douglasii and heracleoides, except for south central WA (var sublineare) when lower growing much like douglasii but often with revolute leaf margins. Flowers are often compound umbels with a leafy bract around the base, red in bud opening bright yellow. https://www.inaturalist.org/observations/163335630 and https://www.inaturalist.org/observations/165614783. ID notes: https://www.inaturalist.org/observations/160463297
E. strictum - similar to E. niveum, but with no leafy bract on flower stem, see below. Also often has much longer petioles (up to 4x leaf length) than E. niveum, though I think that character overlaps.Usually flowers somewhat earlier than niveum, starting in May in cool year, April in warm year (WA), latest flowers in August. If flowers are creamy to bright yellow, nearly always strictum. Burke comments also suggest this is the common one on rocks and lithosol, with E. niveum usually in deeper sandier soil. Leaf habit usually lower and sometimes looking more like a large E. ovalifolium with longer petioles. Flowers often more yellow than niveum. Usually less branched flower stems than niveum. Inner whorl petals (tepals) narrower than outer petals (same as E. niveum). https://www.inaturalist.org/observations/165599598
E. thymoides - easy to recognized from small neat rounded habit and thymelike leaves. sometimes old plants sprawl and have a larger woody base but the growing parts still have the neat habit. This and E. douglasii are often found in very rocky shallow soil (scabland).
E. umbellatum - highly asymmetric tepals, flowers usually yellow but sometimes cream or with some red. https://www.inaturalist.org/observations/120446928
E. niveum and E. strictum are similar but most reliably differentiated by the leafy bract at the flower branches in E. niveum (inconspicuous and threadlike in E. strictum).
Burke: "The leafy bracts below the flowers throughout the inflorescence separates E. niveum from the similar E. strictum, which has no leafy bracts." JHT adds - the bract leaves are smaller than the basal leaves but similarly hairy and silver in tone.
https://burkeherbarium.org/imagecollection/photo.php?Photo=wtu041148&Taxon=Eriogonum%20niveum&SourcePage=taxon
Comments and links on iNat:
https://www.inaturalist.org/observations/724985
From jdjohnson:
"Dimorphic tepals means that three tepals are wide and three tepals are narrow. If you find a close-up photo of Eriogonum ovalifolium flowers, you can see the difference."
E. ovalifolium: apparent with a good close up of individual flowers that are well opened, and then dimorphic tepals are very clear, e.g. photo 3 of https://www.inaturalist.org/observations/44852252), with the inner whorl much narrower than the outer.
