Twenty-six distinct vegetation types have been described within Craters of the Moon (Day, 1985)
1. Cinder Gardens - Cinder gardens are characterized by a cinder surface and low total plant cover. Common species are dwarf buckwheat), silverleaf phacelia, Douglas Chaenactis), two species of monkey flower, dwarf onion, and bitterroot Lewisia.
2. Low Density Lava Flows - Low density lava flows are generally the youngest in the monument and have relatively low plant cover. Shrubs, which provide less than 5% of total cover, include tansybush, ocean spray, mock orange, dwarf goldenweed, and in favorable microsite, antelope bitter brush and lava phlox. Mountain big sagebrush is common in this vegetation type in the southern parts of the monument. Common forbs are scabland penstemon and desert parsley. Sandberg bluegrass and squirreltail are the most common grasses.
3. Medium Density Lava Flows - medium density lava flows have more plant cover (up to 15%) than low density flows, but species composition is very similar. Additional grasses are Thurber needlegrass and Indian ricegrass.
4. Mountain Big Sagebrush/Bluebunch Wheatgrass - The mountain big sagebrush/bluebunch wheatgrass type is widespread in the monument and diverse in composition. Mountain big sagebrush is the dominant shrub. Bluebunch wheatgrass is the common grass. Antelope bitterbrush is common throughout this type. North of the highway mountain snowberry and saskatoon serviceberry are common, especially on wetter sites such as ravines and north-facing slopes.
5. Mountain Big Sagebrush/Sandberg Bluegrass - This type occurs on drier sites or those with shallower soil than type 4, and there is generally more bare ground. In addition to the two dominants named, rabbitbrush, antelope bitterbrush, lava phlox and several species of buckwheat are common. Squirreltail and bluebunch wheatgrass are common grasses on favorable microsites.
6. Mountain Big Sagebrush/Needlegrass - The mountain big sagebrush/needle grass type is found on sandy, often shallow soils in the southern portions of the monument. Mountain big sagebrush dominates; antelope bitterbrush also is common. Needle and thread, squirreltail, and Indian rice grass are common grasses.
7. Mountain Big Sagebrush/Needle-and-thread/Cheatgrass - This type is confined to the south-facing slope at the mouth of Little Cottonwood Canyon.
8. Mountain Big Sagebrush/Idaho Fescue - This type is found on the north and northeast-facing slopes in Little Cottonwood Canyon and on Carey Kipuka. Mountain Big sagebrush occurs in sporadic clumps and at lower densities than in the mountain big sagebrush/wheatgrass type. Herbaceous vegetation, which is relatively dense between shrubs, is dominated by Idaho fescue and prairie junegrass. Scarlet painted-cup and silvery lupine are common forbs. In Carey Kipuka, the dominant sagebrush is basin big sage brush, but it was included in this type for simplicity.
9. Big Sagebrush/Cheatgrass - The big sagebrush/cheatgrass type, which occurs on Carey Kipuka, appears to be a relatively stable successional stage of the big sagebrush/Idaho fescue type.
10. Complex of Type 4 and 8 - Type 10, a complex of types 4 and 8, which is found in Little Cottonwood canyon, contains all species common in both the mountain big sagebrush/bluebunch wheatgrass and the mountain big sagebrush/Idaho fescue types.
11. Three-tip Sagebrush/Idaho Fescue - The three-tip sagebrush/Idaho fescue type occurs on the relatively steep north-facing slopes in upper Little Cottonwood Canyon. Three-tip sagebrush is the dominant shrub, but it occurs in low densities. Forbs in this type include silvery lupine, pussytoes, stonecrop, and Hood's phlox. Idaho fescue, prairie junegrass, and Sandberg bluegrass are common grasses.
12. Early Low Sagebrush/Idaho Fescue - This type is restricted to a small but distinct area on Carey Kipuka. Early low sagebrushis the dominant shrub. Narrowleaf pussytoes, mat eriogonum, and Hood's phlox are common forbs. Idaho fescue is the dominant grass, with sqirreltail common.
13. Low Sagebrush/Sandberg Bluegrass - Low sagebrush/Sandberg bluegrass type occurs on exposed, windswept ridges along Little Cottonwood Canyon. The total plant cover is less than 40%. Low sagebrush is the only shrub present in most areas. Stemless goldenweed, Hood' phlox, rabbit-foot crazyweed, mat eriogonum, and paintbrush are common forbs. Sandberg bluegrass is the dominant grass, with spikegrass common at higher elevations.
14. Low Sagebrush/Idaho Fescue - The low sagebrush/Idaho fescue type is found on site similar to those containing type 13, but on finer textured and/or deeper soil. Idaho fescue replaces Sandberg bluegrass in this type. The total cover is higher than type 13.
15. Complex of Types 13 and 14 - Type 15, is found on exposed ridges. It is composed of mosaics of the low sagebrush/Sandberg bluegrass and low sagebrush/Idaho fescue types. In the national natural landmark theme study, this vegetation type was judged to be an outstanding example of the low sagebrush/Idaho fescue subtheme of the low sagebrush theme.
16. Antelope Bitterbrush - The antelope bitterbrush type covers large areas of the larger cones. Plant cover is generally more than 50%. Antelope bitterbrush is the dominate shrub. Rubber rabbit brush and wax currant are common shrubs. Limber pine and mountain big sagebrush are scattered in this type. Common forbs are Anderson larkspur, sulfur buckwheat, dwarf buckwheat, dwarf monkeyflower, and silverleaf phacelia. Squirreltail, Thurber needlegrass, and Sandberg bluegrass are the common grasses.
17. Antelope Bitterbrush/Great Basin Wildrye - The antelope bitterbrush/Great Basin wildrye type is found on the slopes of medium-aged and older cinder cones. The dominate shrub is antelope bitterbrush with rubber rabbitbrush, mountain snowberry, and Wyeth eriogonum common. Arrowleaf balsamroot, Holboell rockcress, sulfur buckwheat, and stoneseed are common forbs. Desert parsley forms the relatively dense understory where grass density is low. Great Basin wildrye is the most conspicuous grass, but bluebunch wheatgrass occurs in greater density in some areas.
18. Bluebunch Wheatgrass/Idaho fescue - The bluebunch wheatgrass/Idaho fescue type occurs in limited areas on north-facing slopes at upper elevations in Little Cottonwood canyon. Because of snow accumulation, these areas are apparently more mesic than areas that contain shrubs. Forbs present are those from both the mountain big sagebrush/bluebunch wheatgrass and the three-tipped sagebrush/Idaho fescue types.
19. Bluebunch wheatgrass/Sandberg Bluegrass - The bluebunch wheatgrass/Sandberg bluegrass type occurs on three older cones in the Craters of the Moon Wilderness: Round Knoll, Two-point Butte, and Coyote Butte. Inconspicuous shrubs are dominated by low growing forms such as lava phlox and slenderbrush eriogonum.
20. Great Basin Wildrye - The Great Basin wildrye type, which is dominated by relatively dense stands of Great Basin wildrye, is found on alluvial fans where drainages of the Pioneer Mountains enter the lava plains. There is occasional mountain big sagebrush and rubber rabbitbrush. Several forbs are present among the wildrye, including whitestem mentzelia and shepherd';s purse.
21. Limber Pine/Antelope Bitterbrush (low total cover) - Areas containing limber/antelope bitterbrush (low total cover) are composed of large, block type lava remnants interspersed with cinder gardens: for example Devil';s Orchard. Limber pine is common at favorable microsites such as around edges of lava blocks where moisture accumulates. The dominate shrub is antelope bitterbrush; rubber rabbitbrush, tansybush, mountain big sagebrush, lava phlox, and wax currant are also common. Common forbs are dwarf monkeyflower, deceptive groundsmoke, rosy calyptridium, sulfur buckwheat, and dwarf buckwheat. Thurber needlegrass, squirreltail, Indian ricegrass, and Sandberg bluegrass are common grasses. Cinder patches are dominated by species typical of the cinder garden vegetation type.
22. Limber Pine/Antelope Bitterbrush (High Total Cover) - The limber pine/antelope bitterbrush (high total cover) type is found on medium-aged cinder cones. Because lava blocks are absent, the total vegetative cover is higher than type 21. The dominant antelope bitterbrush is a relatively low form. Rubber rabbitbrush and wax currant are common. Mountain big sagebrush is common on favorable soil sites. Forbs and grasses common in type 21 are also common in this type, except for Indian ricegrass.
23. Limber Pine/Antelope Bitterbrush (High Density Limber Pine) - In the limber pine/antelope bitterbrush (high density limber pine) vegetation type, limber pine occurs in relatively high density on favorable north to east-facing slopes of cinder cones. The number of species is similar to type 22, but Douglas-fir is present on older or mesic sites such as Silent Cone. Mountain snowberry and common chokecherry are present with Douglas-fir.
24. Douglas-fir/Mountain Snowberry - The Douglas-fir/mountain snowberry type occurs on relatively steep north-facing slopes of older cinder cones and along Little Cottonwood Canyon. Douglas-fir dominates, with occasional individuals of limber pine. More than half of the soil surface is litter. Mountain snowberry dominates the understory. Common chokecherry is common, especially where light intensity is higher. Willow is present. Common forbs are broadleaf bluebells, sharpleaf valerian, and sticky cinquefoil. Common grasses are Sandberg bluegrass, Idaho fescue, and slender wheatgrass.
25. Upland Quaking Aspen - The upland quaking aspen type occurs on upland sites away from permanent stream courses. Quaking aspen is the dominate tree. A dense layer of forbs and grasses make up the understory with the occasional mountain snowberry and willows. Forbs include sticky purple geranium, scarlet painted-cup, silvery lupine, and Sitka columbine. Common grasses are Kentucky bluegrass, slender wheatgrass, Nelson's needlegrass, and Idaho fescue.
26. Riparian - The riparian type differs from the quaking aspen type by the presence of dense woody vegetation, proximity to a permanent watercourse, and the presence of a dense layer of tall forbs. The dominate trees form a mosaic consisting of patches of aspen, black cottonwood, common chokecherry, willow, mountain alder, and bog birch. The last 3 species are more common at higher elevations. A dense tall forb element is conspicuous in mesic areas; this is dominated by cow parsnip, bigsting nettle, and small-leaf angelica. Blackhead coneflower, nettle-leaf horsemint, and Sitka columbine are also common.