Leaves alternate or rarely opposite, simple or compound; lamina often large and highly dissected; petiole often broadened and sheathing at base, rarely with stipules.
Inflorescence terminal or axillary, sometimes leaf-opposed, usually compound, or sometimes a simple umbel or head or reduced to 1 or a few flowers; umbels usually with bracts (involucre) and umbellules with bracteoles (involucel) at their bases. Flowers actinomorphic, 5-merous, bisexual or unisexual and the plants monoecious, polygamous or rarely dioecious; floral parts epigynous. Sepals 5 and small or absent. Petals 5, valvate or somewhat imbricate in bud. Stamens 5; anthers 2-locular, introrse, dehiscing by longitudinal slits. Carpels rarely 1, usually 2 joined to form a 2-locular inferior ovary; styles 2, free, swollen at base to form a nectariferous disk (stylopodium); ovules pendent, 1 per loculus.
Fruit dry, separating at maturity from the central axis (carpophore) into 2 indehiscent mericarps; mericarps often flattened laterally or dorsally and with 5 conspicuous or inconspicuous longitudinal ribs and often secondary ribs and furrows between them, the surface smooth, ornamented or sometimes hairy; seeds with endosperm, embryo minute.
| | Key to the family APIACEAE | |
| 1 | Leaves segmented by transverse septa | 2 |
| 2 | Inflorescence compound | Aciphylla |
| 2* | Inflorescence of simple umbels | Lilaeopsis |
| 1* | Leaves not segmented by transverse septa | 3 |
| 3 | Flowers in more or less sessile heads surrounded by large or conspicuous bracts or bracteoles | 4 |
| 4 | Leaves and bracts spinose, or with prickles on margins | Eryngium |
| 4* | Leaves and bracts not spinose | 5 |
| 5 | Leaves stem-clasping, simple | Bupleurum |
| 5* | Leaves not stem-clasping, deeply dissected or compound | 6 |
| 6 | Fruit pubescent to villous, mericarps smooth | Actinotus |
| 6* | Fruit glabrous; mericarps finely ribbed | Xanthosia |
| 3* | Flowers stalked, in umbels; bracts or bracteoles less conspicuous or absent | 7 |
| 7 | Flowers in simple umbels or few-flowered irregular compound or contracted umbels | 8 |
| 8 | Leaves deeply dissected or compound | 9 |
| 9 | Fruit with 2 horizontally spreading apical appendages | Uldinia |
| 9* | Fruit lacking apical appendages | 10 |
| 10 | Leaves pinnately dissected | 11 |
| 11 | Leaves in basal rosette; umbels spreading, long-pedunculate; mericarps 5-ribbed | Oreomyrrhis |
| 11* | Leaves cauline, alternate; umbels more or less globose, very shortly pedunculate; mericarps of 2 types, tuberculate and long-bristly | Torilis |
| 10* | Leaves ternately or palmately dissected or tripartite | 12 |
| 12 | Leaves with scarious stipules; plants stoloniferous | Hydrocotyle |
| 12* | Leaves without stipules; plants with taproot or woody rootstock | 13 |
| 13 | Leaves subsessile or very shortly petiolate; sepals prominent; mericarps 7–9-ribbed | Xanthosia |
| 13* | Leaves with long petioles; sepals minute; mericarps hairy, tuberculate or rarely indistinctly 5-ribbed | Trachymene |
| 8* | Leaves simple or lobed, not deeply dissected or compound | 14 |
| 14 | Leaves more or less circular in outline or reniform | 15 |
| 15 | Plants with fleshy taproot or rhizomatous; leaves in a basal rosette | 16 |
| 16 | Flowers in a regular simple umbel; petals yellow-green | 17 |
| 17 | Leaves with scarious stipules, partly fused to petiole, acuminate or laciniate above; umbels 4–8-flowered; bracts ovate, fused at the base | Schizeilema |
| 17* | Leaves without stipules, the petiole sheathing at the base; umbels 10–20-flowered; bracts linear, free to base | Diplaspis |
| 16* | Flowers in an irregular simple or compound umbel; petals white | Dichosciadium |
| 15* | Plants stoloniferous or erect or ascending with branched stems; leaves not in a basal rosette | 18 |
| 18 | Leaves with scarious stipules; mericarps smooth to rough or tuberculate between ribs | Hydrocotyle |
| 18* | Leaves without stipules; mericarps reticulate-patterned between ribs | Centella |
| 14* | Leaves spathulate or ovate in outline | 19 |
| 19 | Leaves in basal rosette; peduncles long, erect | 20 |
| 20 | Leaves ovate, obtusely lobed; fruit oblate, laterally compressed, the mericarps smooth or minutely tuberculate. (Trachymene humilis) | Trachymene |
| 20* | Leaves spathulate, acutely toothed at the apex, fruit ovoid, the mericarps evenly ribbed | Oschatzia |
| 19* | Leaves alternate on branching stems; peduncles short, often reflexed. (Xanthosa tridentata) | Xanthosia |
| 7* | Flowers in compound umbels, usually many-flowered | 21 |
| 21 | Fruit with a conspicuous beak to c. 7 cm long | Scandix |
| 21* | Fruit without a beak | 22 |
| 22 | Bracts and bracteoles absent or when present few and inconspicuous | 23 |
| 23 | Leaflets broad-elliptic or ovate, with toothed margins | 24 |
| 24 | Petals yellow; bracts and bracteoles sometimes present; fruit elliptic, conspicuously winged | Pastinaca |
| 24* | Petals white or pink; bracts and bracteoles absent; fruit ovoid, ribbed, not winged | Aegopodium |
| 23* | Leaflets ovate-cuneate or lanceolate with lobed margins, or linear or filiform | 25 |
| 25 | Ultimate leaf segments filiform, less than 0.5 mm wide | 26 |
| 26 | Fruit more or less elliptic; mericarps with slender dorsal ribs, the lateral ribs winged | Anethum |
| 26* | Fruit oblong-ovoid or ovoid-globose; mericarps with 5 equally prominent ribs | 27 |
| 27 | Umbels terminal; bracts sometimes present; petals yellow or yellow-green; fruit oblong-ovoid, 4–10 mm long | Foeniculum |
| 27* | Umbels leaf-opposed; bracts absent; petals white; fruit ovoid to globose, 1–3 mm long | Ciclospermum |
| 25* | Ultimate leaf segments more than 1 mm wide | Apium |
| 22* | Bracts and bracteoles always present | 28 |
| 28 | Fruit with spines | Daucus |
| 28* | Fruit without spines | 29 |
| 29 | Leaves undivided, lobed or 3-foliolate | Platysace |
| 29* | Leaves pinnately compound, 1–4-pinnatisect or ternatisect | 30 |
| 30 | Rays more than 20 per inflorescence; bracts 3-fid or pinnatisect | Ammi |
| 30* | Rays less than 20 per inflorescence; bracts lanceolate to subulate, undivided | 31 |
| 31 | Fruit ovate, oblong or ellipsoid, more than 5 mm long | Gingidia |
| 31* | Fruit globose to ovoid, less than 5 mm long | 32 |
| 32 | Leaves 1-pinnate, the leaflet margin toothed | Berula |
| 32* | Leaves 2–3-pinnate, the leaflet margins lobed | Conium |
