| | 1. Stem regularly branched |
| |
| | 2. Basal internode of branch > subtending nodal sheath |
| 2 E. arvense |
| | 2' Basal internode of branch < subtending nodal sheath |
| |
| 2 E. palustre |
| | 3' Sheath teeth 14–28 on sterile stem, 20–30 on fertile stem |
| 2 E. telmateia subsp. braunii |
| | 1' Stem unbranched or branches scattered |
| |
| | 4. Stem brown, fleshy, lasting < 1 month irregularly in spring |
| |
| | 5. Sheath teeth 6–14 on sterile stem, 6–10 on fertile stem |
| 2 E. arvense |
| | 5' Sheath teeth 14–28 on sterile stem, 20–30 on fertile stem |
| 2 E. telmateia subsp. braunii |
| | 4' Stem green, firm, lasting > 1 month |
| |
| | 6. Sheath teeth 5–10, persistent |
| 2 E. palustre |
| | 6' Sheath teeth 10–50, generally deciduous |
| |
| | 7. Cone tip pointed; sheath generally with 2 dark bands, 1 at base, 1 at tip; stem perennial herb, generally scabrous |
| E. hyemale subsp. affine |
| | 7' Cone tip rounded; sheath generally with 1 dark band, at tip; stem annual (or perennial herb in s), generally not scabrous |
| E. laevigatum
|