Lomatium Identification
Mostly for species found in western and central Washington State. There are several other species in southeastern Washington that I have not yet observed and are not listed. Be sure to follow links for species - good pictures and often more detailed description. I also have a partial and very simplified key. This guide is somewhat idiosyncratic and mostly focuses on specific characters that I find useful in the field rather than a comprehensive description or key.
Useful non-technical slide show: Slides (this source says that seed dispersal is by water and rodent cache, but I would add wind dispersal, at least for species with fruit wings in the windier parts of central Washington (said winds have nearly dispersed me at times). The winged fruits sure look they are designed to be dispersed by high winds and not otherwise (winged fruits). By molecular studies, Lomatium and Cymopteris (and a few Tauschia and others) are extensively interdigitated, which appears not to have fully penetrated to formal naming. George et al 2014 Phylogenetic Analysis Reveals Multiple Cases of Morphological Parallelism and Taxonomic Polyphyly in Lomatium .
A number of new Lomatium species are present in Washington, some of them just published or in the process of description and publication, so if you see one that looks really unusual, I suggest pinging Mark Darrach of the Burke Herbarium (type "@lomatiumlarry" in a comment box).
Some identification guides suggest crushing some leaves, but all of the species I have tested seem to smell roughly the same of cedar and turpentine, so smell can be useful to identify as Lomatium but not among species (on the other hand I do not have a discriminating nose).
Photo tips
A few Lomatiums can be identified by a single photo but most cannot.
Take several photos, possibly including:
1) the overall plant (not just the flower) and perhaps a text comment on size
2) the leaf structure (holding your hand or a sheet of something behind the leaf helps)
3) the underside of the secondary umbel (the base of each little cluster of flowers)
4) as close as you can get to a leaflet and the flower stem (some species have short hairs). Newer phones often have macro capability that is quite good.
5) a shot toward the base trying to focus on whether leaf stems come straight out of the ground (basal leaf) or branch off from the flower stem above ground (cauline leaf).
6) Do NOT bother posting lots of shots of the top of the flowers: one is plenty because other than color and general arrangement of the umbel they all look nearly identical. For the Computer Vision Model multiple shots are likely even detrimental because they will dominate the training set.
Guide
[ ] names mean "easily confused with"
Cymopterus terebinthinus - except when fruiting looks a lot like a medium to large leafy yellow Lomatium with highly dissected shiny leaves with a sharp tipped leaflet. In WA state often found in dry sandy (sometimes rocky) soils and slightly sticky/shiny leaves and stems may have sand grains stuck on them. Mature fruit with multiple wing-like ridges and even during late flowering the basic ridged structure is apparent under each flower. Observation.
L. ambiguum - [triternatum] yellow medium small to tall lanky glabrous Lomatium with highly divided leaves mostly on floral stem with leaflets often looking ill-formed with irregular sized rounded lobes (reminiscent of moose antlers Observation). Flowers mid spring, no involucre or involucel (umbel bracts), umbels usually multiple and well separated when mature. Lacks short fuzzy flower stem hairs characteristic of L. triternatum, but requires good closeup photo or hand lens. Mostly absent from south central WA, where triternatum is common. Observation.
L. brandegeei - montane, medium to largish, deeply divided leaves, medium to narrow width leaflets with highly visible veination, yellow flowers, glabrous flower stem, very common in developed serpentine soil in Wenatchees (and more widely in dry side central to northern Cascades) despite being listed as vulnerable. Observation and Observation.
L. canbyi - often on shallow lithosol, small early flowering white with distinctive widish leaflets, usually glaucous/grayish/bluish and held close to flat in plane of leaf, often quinate division, often with a tiny cusp on leaflet tip. Contrary to Burke, I find the involucel lobes are often quite prominent, but sometimes thin and whispy. Flower stems usually brownish red. Mature fruits very flattened and green with red edges (eventually brown). Mostly on Columbia Plateau from low to moderate elevations. Observation and Observation.
L. columbianum - large and bushy with rosy-pink flowers, unmistakable when in flower and even after. Huge fruits for a Lomatium. Observation and Observation and Fruits.
L. cous - small yellow, not yet observed by me. Found in the southeast corner of Washington (and elsewhere). Burke.
L. cuspidatum - narrow range, Wenatchee serpentine specific, distinctive leaves, dark purple/red flowers. Mature fruits somewhat flattened but have no wings or narrow wings. Detailed description.
L. dissectum - [multifidum] large bushy, dark red/purple (sometimes yellow) flowers, wider leaflets than L. multifidum. Leaflets often appear roughened probably due to very short trichomes.Observation.
L. farinosum - very early flowering, often on shallow lithosol, very small yellow (or white?) glabrous with narrow branched leaves. Distinctive leaves with each side branch in three parts (biternate), linear leaflets folded into V- to U-shaped cross-section, sometimes flattened out some when older. At maturity most leaflets have a tapered reddish/brown tip (Observation, also found in L. triternatum). Involucel lobes prominent and often fused at bases. Mature fruits somewhat flattened but have narrow wings. All the ones I have seen are on scabland (shallow lithosol) where they can be locally abundant. Observation (early) ; Observation (mid-flower).
L. frenchii - [watsonii] possibly will be the name of a glabrous L. watsonii-like species present in south central WA in the east side mountains, around Naches and probably elsewhere. Comparison of L. watsonii and possible L. frenchii leaves.
L. geyeri - [gormanii, piperi] medium small, white flowers with fairly narrow leaflets, larger and more leaves than L. gormanii and usually growing in deeper soil on the Columbia Plateau and hills. Has a distinctive double root bulge (Burke). I am fairly sure this also common in the high eastern Wenatchees in exposed sites. Observation.
L. gormanii - [piperi] very early flowering, widespread tiny plant, white flowered, glabrous, with no flower stem leaves (unlike piperi), sometimes locally abundant on shallow lithosol. Mature fruits somewhat flattened but have very narrow wings. Observation.
L. hallii - small to medium, yellow flowers, found in Oregon including Siskiyous. Observation.
L. howellii - uncommon, distinctive wide toothed leaflets, mostly on Klamath serpentine. Observation.
L. klickitatense - [papilioniferum] large puffy finely dissected, leaflets longer than L. papilioniferum, yellow flowers. Observation and Observation.
L. knokei - very rare medium small yellow with narrow leaflets. Possible observation.
L. laevigatum - very narrow range mostly in Columbia Transect, large yellow with long leaflets, involucel nearly absent. Observation.
L. leptocarpum (L. bicolor leptocarpum) - not yet observed by me. Observations by others.
L. linearifolium - [gormanii, piperi] very similar to L. gormanii, main obvious difference is elongated flower head. I have not observed this one. Mostly in southeastern WA. Burke.
L. lithosolamans - very early flowering white, on shallow lithosol, uncommon but possibly locally abundant on extreme lithosol, usually with very few leaflets that are V-shaped in cross section unlike other early salt and peppers. Leaves few and rather fleshy and often persist and retain shape until completely dry and brown. Flower umbel sometimes appears elongated. Fruits ridged but lacking obvious wings, usually turning purplish near maturity. Endemic to Kittitas/Yakima Counties. Observation by kimberlyq and (fruiting/dried leaves) observation.
L. macrocarpum - widespread and common especially on Columbia Plateau, sometimes on shallow lithosol, medium sized, ground hugging when in early flower (later more erect and when in fruit the stems are often very erect, towering over the shriveling leaves), easily recognized green-white flowers with long white anthers (often yellow flowers further south), velvet-hairy floral stalks and bracts, cusped leaflet tips, sometimes has quinate leaf division, ASYMMETRIC secondary umbel bracts (involucels) longer on outer hemisphere. Observation.
L. martindalei - moist montane, small, usually prostrate, wide leaflets, yellow flowers. On west side of Cascade Ridge, or close such as Goat Rocks or Mount Aix. Can be confused with Sanicula graveolens (look at the umbel bracts) and L. watsonii (look for hairy leaves). Observation.
L. multifidum - [dissectum, thompsonii] large bushy highly dissected leaf, yellow flowers (sometimes dark red), very similar to L. dissectum but narrower leaflets. Often has minute hairs or papillae on leaves. Observation.
L. nevadense - central to southern Oregon and further east and south, somewhat similar to canbyi.
L. nudicaule - sometimes montane, medium to large, unmistakeable very broad leaflets, yellow flowers, large swollen base where umbels branch. Leaflets sometimes have toothed tip.Observation.
L. papilioniferum - large showy yellow flowered (smaller in stunting habitats), distinctive highly dissected leaves with short terminal leaflets, dissections appear angular, leaves often rough looking or with very short hairs. Foliage looks "frothy" from a distance. One of few on rock cliffs, extremely common in Columbia transect but widespread in eastern WA. Observation.
L. piperi - see L. gormanii. Tends to be at higher elevations (I think) and more often on clay soils. If there are many plants locally, digging up a root distinguishes - piperi has many rootlets on the globose tuber. Observation.
L. quintuplex - on shallow lithosol, small yellow flowered with highly dissected leaves in a strongly 3-D shape and slightly cusped nearly cylindrical leaflets (photo), in marginal rocky sites where it is often very abundant. Mature fruits somewhat flattened but have no wings or narrow wings. Narrow range in Kittitas and Yakima counties. Observation.
L. refugianum - [roneorum, but ranges distinct] not yet published. Yellow flowered, highly dissected glaucous to medium green leaves with short slightly thickened leaflets. Involucels narrow to inconspicuous or absent. Flower stems glabrous. Leaflet and leaflet stems with very short triangular papillae making the surface look rough if you look closely. Probably a narrow endemic, type locality Bethel/Burnt Mountain Ridge east of Mt. Rainier near Naches. Observation and Closeup of tiny papillae.
L. roneurum - [refugianum, but ranges distinct] rare, distinctive thick leaflets, medium sized, yellow flowers sometimes with red flush, narrow range on Chumstick and adjacent gneiss rocks. Observation and Observation.
L. simplex - [triternatum] hard to distinguish from narrow-leaved forms of L. triternatum. lanky medium sized yellow, two to three times ternate narrow leaflets, often very long leaflets. Velvet-like hairy. Does NOT have leaves growing out of flower stem (unlike many triternatum). Observation.
L. thompsonii - [brandegeei, multifidum] narrow endemic in east Wenatchee Mountains. Medium to large bushy yellow, elongated fruits. Rather lacy looking with highly branched leaves and narrow flat leaflets. Very short velvety hairs on all stems and fruit (might need a hand lens or very closeup photo). Mostly in East Wenatchee mountains above Wenatchee in Blewett Pass to Stuart Ridge area. Can be confused with L. brandegeei or L. multifidum. Observation.
L. triternatum - highly variable in size and leaflet width. Very common east of the Cascade ridge. Small to medium sized, yellow to pale yellow, narrow leaflets (narrowly lanceolate to nearly linear, except broader in var. brevifolium). Narrowest-leafed forms hard to distinguish from L. simplex. Dense very short hairs on flower and umbel stems (may be hard to photograph because they are so short), sometimes has reduced leaf on flower stem (unlike simplex), often disorganized looking leaves, lacking the specific 3-D structure found in many Lomatiums. Observation.
L. tuberosum - on coarse basalt talus/scree, rare adorable plant, very distinctive terete foliage often with bluish color, dark yellow flowers. Observation and immature fruits.
L. utriculatum - small lowland coastal, yellow flowers early spring, highly dissected leaves with narrow leaflets. Observation and umbel details.
L. watsonii - [frenchii] small yellow to very pale yellow flowered, hairy leaves, somewhat similar to L. canbyi (widespread) and L. cous (found only in SE corner). Mostly from Wenatchee Mountains to south central WA often at high elevations among large rocks or on rocky soil on exposed sites. Ground hugging while in flower (at least in the windy exposed sites where I have seen it). Leaves with dense short hairs (possibly the glabrous form will be split off as L. frenchii). Partially or fully fused involucel. Flower stems sometimes wooly/hairy, umbel stems and immature fruits often hairy. Burke. Observation.
Lomatium nova 1 - nudicaule-like https://www.inaturalist.org/observations/219212523
Lomatium (possible) nova 2 - knokei-like https://www.inaturalist.org/observations/218263367
