Helvella key
| Key slightly modified from an published document authored by Brian Spooner (Kew). | ||
| 1 | Stipe ribbed and furrowed over its entire length, internally solid or chambered, sometimes very short, but with ribs often present on the underside of the cap | 2 |
| Stipe not ribbed (occasionally slightly grooved at base and/or apex), always well-developed | 9 | |
| 2 (1) | Cap cupulate; stipe internally solid or chambered (section Leucomelaenae) | 3 |
| Cap saddle-shaped or irregularly lobed and convex; stipe internally chambered (section Helvella) | 6 | |
| 3 (2) | Ribs on stipe extending conspicuously to the underside of the cap, usually to at least half way | 4 |
| Ribs on stipe not or scarcely extending to the underside of the cap | 5 | |
| 4 (3) | Hymenium brown to dark brown, sometimes with a violet tinge. Cap externally dark brown above, paler below. Ribs of stipe branching, usually sharp-angled, rarely interconnected by cross-veins, not reaching the margin of the cap. Fruiting in spring | H. acetabulum |
| Hymenium grey-brown. Cap externally paler to margin. Ribs of stipe blunt, branching and often interconnected by cross-veins, often reaching the margin. Fruiting in summer and autumn (June to September) | H. costifera | |
| 5 (3) | Stipe short and broad, often indistinct, less than 1cm long, at least 8mm wide. Asci without croziers. Submature spores generally not present when most are mature | H. leucomelaena |
| Stipe distinct, usually longer than 1cm & less than 7mm wide above. Ascus bases forked, with croziers. A mixture of mature and submature spores often present | H. solitaria | |
| 6 (2) | Hymenium whitish to cream; outer surface villose (distinctly hairy); edge of cap free from stem | H. crispa |
| Hymenium grey-brown to blackish; outer surface smooth or at most finely pubescent; edge of cap free or in part fused with stem | 7 | |
| 7 (6) | Stipe and outer surface pale greyish to nearly black. Cap saddle-shaped; edge of cap fused in part with the stipe. Outer surface smooth | H. lacunosa |
| Stipe and outer surface whitish to pale brown. Cap saddle-shaped or slightly convex to lobed, edge of cap free or fused in part with the stipe. Under surface of cap covered with a network of raised veins, outer surface smooth or finely pubescent | 8 | |
| 8 (7) | Cap saddle-shaped to irregular in form, 1.5 - 4 cm broad; edge of cap fused in part with the stipe. Ascospores 17 - 21 x 11 - 13 µm in size. Associated with Populus spp. | H. fusca |
| Cap simple, convex or lobed, 0.5 - 2 cm broad; edge of cap free from stem. Ascospores 15 - 17 x 10.5 - 12 µm in size. On calcareous soil in various places | H. phlebophora | |
| 9 (1) | Hymenial region cupulate; outer surface of cap villose | 10 |
| Hymenial region saddle-shaped or convex and irregularly lobed; outer surface of cap villose or smooth (section Elasticae) | 13 | |
| 10 (9) | Ascospores ellipsoidal-fusiform, to 27 µm long (section Macropodes) | H. macropus |
| Ascospores with broadly rounded ends, to 22 µm long (section Cupuliformae) | 11 | |
| 11 (10) | Entire fruit-body blackish, outer surface villose, sometimes white-villose towards the margin of the cap. Fruiting in spring | H. corium |
| Fruit-body not totally blackish, either stipe or hymenium or whole fruit-body grey or cream; outer surface pubescent or villose. Fruiting in autumn | 12 | |
| 12 (11) | Hymenium and underside cream to yellowish; stipe cream. Cap usually < 1 cm diam. | H. cupuliformis |
| Hymenium and underside grey to grey-brown; stipe whitish to grey or brown. Cap commonly > 1 cm diam. | H. dissingii | |
| 13 (9) | Hymenium and stipe dark brown to black, underside of cap grey or grey-brown | 14 |
| Hymenium and underside of cap whitish to grey or brown, stipe whitish to pale grey-brown | 15 | |
| 14 (13) | Outer surface of cap usually darker, grey-brown, markedly villose. Margin inrolled over hymenium | H. pezizoides |
| Outer surface of cap usually paler, grey, glabrous to very finely pubescent. Margin reflexed towards stipe | H. atra | |
| 15 (13) | Hymenial margin reflexed towards the stipe and sometimes fused with it | 16 |
| Hymenial margin inrolled, never fused with the stipe | 17 | |
| 16 (15) | Hymenium pale brown to brown, darker when dry, cap campanulate to simple saddle-shaped. Stipe slender, whitish to cream, finely pubescent. In woodland, fruiting in summer or autumn | H. elastica |
| Hymenium dark brown to blackish, sometimes with purplish tinges when fresh, complex saddle-shaped. Stipe robust, white to pale grey, glabrous. In sand dunes, fruiting in spring | H. leucopus | |
| 17 (15) | Outer surface of cap and stipe markedly villose | H. epihippium |
| Outer surface of cap smooth or finely pubescent; stipe pubescent to villose | 18 | |
| 18 (17) | Hymenium whitish to fawn or pale brown, not drying black; stipe pubescent to villose | H. latispora |
| Hymenium dark grey or grey-brown to blackish, drying black; stipe pubescent | H. albella | |
Taxonomic term: