1	Plants dioecious	2
–	Plants hermaphrodite	3
2	Cauline leaves with pinnae in 6–25 primary pairs; primary pinnae linear to lanceolate, recurved; terminal pinnae 7.8–30.0 × 0.9–2.9 mm, lateral pinnae 8.0–28.9 × 0.8–2.7 mm; petals present or absent, those of ♂ flowers 1.5–2.2 mm long, those of ♀ flowers 1.2–1.5 mm long	Lepidium sisymbrioides Hook.f.
–	Cauline leaves with pinnae in 14–32 primary pairs; primary pinnae linear, obovate to broadly oblong, not recurved; terminal pinnae 3.0–16.0 × 1.0–4.9 mm, lateral pinnae 2.6–11.3 × 0.8–3.9 mm; petals usually absent, if present those of ♂ flowers 1.3–1.5 mm long, those of ♀ flowers 0.8–1.1 mm long	Lepidium solandri Kirk
3	Silicle reticulate or warty; valves indehiscent or breaking into two 1-seeded segments (not splitting along valves)	4
–	Silicle smooth or papillate, glabrous or hairy; dehiscing by 2 valves to leave a persistent replum	6
4	Plants rhizomatous; stems erect up to 0.6 m tall; stems and leaves covered in short, arching hairs; leaves simple, glaucescent; pedicel > 3× silicle length; style > 1.0 mm long	*Lepidium draba L.
–	Plants tap-rooted without rhizomes; stems decumbent up to 1m long; stems and leaves glabrous, papillate or sparsely hairy on petioles of basal leaves, hairs if present spreading; leaves 1–2-pinnatifid, dark green, grass green to yellow-green; pedicel < 2× silicle length; style < 0.5 mm long	5
5	Petals 0 or if present < sepals, up to 0.5 mm long; stamens 2–4; pedicel ≥ silicles; silicles 1.4–1.7 mm long, apex notched, dehiscent at maturity, valves reticulate and ridged or finely warty; style ± sessile	*Lepidium didymum L
–	Petals > sepals, 1.0–2.0 mm long; stamens 6; pedicel ≤ silicles; silicles > 2 mm long, apex apiculate, indehiscent, valves coarsely warty, corky; style up to 0.5 mm long	*Lepidium coronopus (L.) Al-Shehbaz
6	Silicle apex acute (not notched)	7
–	Silicle apex notched	8
7	Mid and upper stem leaves acuminate, teeth acicular-acerose; pedicels minutely hairy	Lepidium castellanum de Lange et Heenan
–	Mid and upper stem leaves not acuminate, teeth acute or subacute, not acicular-acerose; pedicels glabrous	Lepidium oleraceum G.Forst. ex Sparrm.
8	Stamens 6	9
–	Stamens 2 or 4	12
9	Leaves, stems and pedicels glabrous; stamens 2–4–6; leaf base attenuate	10
–	Leaves, stems and pedicels hairy; stamens 6; leaf base amplexicaul	11
10	Cotyledons 3-fid; plant erect; basal and stem leaves pinnatifid; stamens 6; silicles 5.0–9.0 × 3.0–5.0 mm, broadly ovate to elliptic, surface smooth when fresh or dry	*Lepidium sativum L.
–	Cotyledons simple; plant decumbent; leaves simple, toothed; stamens 2–4–6; silicles 3.0–3.8 × 2.8–3.8 mm, broadly orbicular and turgid when fresh, valve surface collapsing on drying to become wrinkled or reticulate	Lepidium oligodontum de Lange et Heenan1
11	Plants annual; silicle densely papillate; style 0.2–0.5(–0.7) mm long, not or only slightly protruding beyond apical notch of silicles; anthers yellow	*Lepidium campestre (L.) W.T. Aiton
–	Plants perennial; silicle not, or sparsely papillate; style (0.6–)1.0–1.5 mm long, protruding well beyond apical notch of silicles; anthers red or violet	*Lepidium heterophyllum Benth.
12	Stamens 2 or 2–4	13
–	Stamens 4	29
13	Plants suberect to erect	14
–	Plants decumbent or prostrate	25
14	Stems papillate, puberulent, or pubescent	15
–	Stems glabrous at least below, rarely with a few hairs above	20
15	Silicles mostly orbicular or obovate (rarely with some broadly elliptic or broadly ovate)	16
–	Silicles ovate, elliptic or rhomboid	18
16	Upper stem leaves pinnatifid, stem hairs spreading	*Lepidium bonariense L.
–	Upper stems leaves entire or toothed; stem hairs strongly recurved	17
17	Silicles obovate, widest above middle; rachis of raceme with straight cylindrical or clavate hairs; petals absent or rudimentary and 0.3–0.9 mm; cotyledons incumbent	*Lepidium densiflorum Schrad.
–	Silicles orbicular, widest at middle; rachis of raceme with curved hairs; petals 1.0–2.5 mm, rarely rudimentary; cotyledons accumbent or rarely incumbent	*Lepidium virginicum L.
18	Young stems and upper leaf margins with small triangular cartilaginous denticles, often paired from a common base; mid-stem leaves oblanceolate to cuneate, margins serrate to dentate; silicles 2.7–3.0 × 2.0–2.3 mm ovate	Lepidium desvauxii Thell. 2
–	Young stems and leaf margins puberulent; mid-stem leaves linear, lanceolate to oblanceolate, entire with marginal hairs, silicles 1.8–5.0 × 1.5–2.5 mm, elliptic, ovate to rhomboid	19
19	Lower and upper stem leaf bases auriculate-sagittate; upper stem leaves linear to lanceolate, usually with lateral 1–2 teeth in upper ⅓, apex acute; silicles 2.5–5.0 × 1.5–2.5 mm, ovate to narrowly rhomboid; petals minute	*Lepidium hyssopifolium Desv.
–	Lower and upper stem leaf bases attenuate; upper stem leaves linear, entire, apex obtuse to subacute; silicles 1.5–3.0 × 1.5–2.3 mm, elliptic; petals absent.	*Lepidium ruderale L.3
20	Basal leaves simple, lanceolate to oblanceolate (very rarely with some leaves pinnatifid), margins serrate (sometimes deeply lacerate), occasionally with 1–2 lobes, lobes linear entire.	21
–	Basal leaves pinnatifid or lyrate-pinnatifid, lobes linear, distal margins of lobes serrate or dentate (rarely entire)	23
21	Flowers with (2–)4 stamens; silicles 2.5–3.5 × 1.5–3.3 mm, orbicular to orbicular-rhomboid, minutely notched	Lepidium panniforme de Lange et Heenan4
–	Flowers with 2 stamens; silicles 2.0–3.5 × 1.8–2.5 mm, oblong, obovate or elliptic	22
22	Stems ridged or grooved when dry, glabrous or sparsely puberulent; silicles 2.0–2.8 × 1.8–2.0 mm, obovate to elliptic	*Lepidium africanum (Burm.f.) DC.
–	Stems smooth when dry, glabrous near base otherwise puberulent; silicles 3.3–3.5 × 2.2–2.5 mm, oblong	*Lepidium divaricatum W.T.Aiton
23	Cauline leaves mostly auriculate-sagittate at base; pedicels adaxially hairy; silicles 2.0–3.0 × 1.5–2.5 mm	24
–	Cauline leaves attenuate at base; pedicels glabrous (very rarely with scattered hairs); silicles 3.5 × 2.1–2.4 mm	*Lepidium pseudohyssopifolium Hewson
24	Mid cauline leaves lanceolate with serrate / serrulate margins; rosette and lower cauline leaves lyrate-pinnatifid with a large broad terminal lobe; silicles 2.0–3.0 × 1.5–2.0 mm, ovate to elliptic	*Lepidium peregrinum Thell.5
–	Mid-cauline leaves oblanceolate to cuneate, the margins dentate with acute, ± patent lobes, often with only a single pair below apex; rosette and lower cauline leaves not lyrate-pinnatifid; silicles 2.4–3.0 × 1.8–2.5 mm, ovate to rhomboid	*Lepidium pseudotasmanicum Thell.
25	Young stems finely puberulent; hairs dense to sparse, shortly papillate or tapered	26
–	Young stems glabrous	27
26	Rosette and lower stem leaves pinnatifid; racemes 10–50 mm long, leaf-opposed, obscured by surrounding foliage	Lepidium flexicaule Kirk
–	Rosette and lower stem leaves spathulate, oblong or elliptic; racemes 10–90 mm long, not or scarcely leaf-opposed, overtopping surrounding foliage	Lepidium rekohuense de Lange et Heenan
27	Leaves narrowly spathulate, cuneate, obdeltoid, obovate (rarely elliptic-lanceolate), entire or sparingly dentate in upper ⅓; teeth (if present) in 1–3(–5) pairs; silicles broadly orbicular and turgid when fresh	Lepidium oligodontum de Lange et Heenan1
–	Leaves oblanceolate, cuneiform, oblong-obovate, obdeltoid to spathulate, margins finely to deeply incised in upper third to quarter; silicles orbicular, orbicular-ovate to ± rhomboid, cartilaginous (never turgid)	28
28	Plants prostrate; branches numerous, leafy for entire length; leaves finely serrated to crenate, teeth in 10–30 pairs, leaf apices subacute, obtuse to rounded; stamens 2; silicles 2.5–3.5 × 1.5–3.3 mm, elliptic, rhomboid, not winged	Lepidium limenophylax de Lange, B.D.Rance et D.A.Norton
–	Plants decumbent to subascendant, widely spreading; branches numerous, leafy only in upper third; leaves finely to deeply incised in upper third to quarter only, teeth in 3–8 pairs, leaf apices praemorse; stamens 2–4; silicles 2.8–3.3 × 2.4–3.0 mm, orbicular, orbicular-ovate to ± rhomboid, winged	Lepidium oblitum Houliston, Heenan et de Lange6
29	Rosette and/or basal leaves pinnatifid or pinnate	30
–	Rosette and/or basal leavesnot pinnatifid or pinnate	31
30	Plant forming compact, persistent leafy rosettes; flowering stems sparingly leafy, prostrate to ascending; silicles 1.5–2.0 × 1.5–1.8 mm, suborbicular, valves glabrous or sparsely hairy	Lepidium tenuicaule Kirk
–	Plant erect, rosettes not compact, often withering at flowering; flower stems erect, leafy; silicles 2.8–4.0 × 2.3–3.2 mm, broadly elliptic, valves glabrous	Lepidium naufragorum Garn.-Jones et D.A.Norton7
31	Plants decumbent or prostrate	32
–	Plants ascending to erect	38
32	Plants up to 150 mm diameter; stems filiform; leaves 3–6 mm wide, entire, basal leaves dark brown-green (rarely dark green); basal sheath broad, scarious, persistent; silicles 1.5–2.0 × 1.0–1.5 mm	Lepidium kirkii Petrie
–	Plants 0.3–1.0 m diameter; stems stout; leaves 5–46 mm wide, serrate, dentate, crenate, lacerate or sometimes entire (Lepidium oligodontum only), basal leaves green; basal sheath absent or if present, narrow, not scarious or persistent; silicles 2.1–6.4 × 1.5–5.0 mm	33
33	Plants rhizomatous; stems flexuous; silicles 4.9–6.4 × 4.2–4.9 mm	Lepidium obtusatum Kirk
–	Plants not rhizomatous; stems not flexuous; silicles 2.5–4.7 × 1.5–3.9 mm	34
34	Rosette leaves persistent; silicles broadly ovate, ovate to obovate	Lepidium amissum de Lange et Heenan
–	Rosette leaves absent, or withering at flowering; silicles broadly orbicular, orbicular, orbicular-rhomboid to elliptic-rhomboid	35
35	Plants upright to spreading or decumbent or sprawling; leaves broadly elliptic, elliptic-oblanceolate, elliptic-obovate, oblanceolate to lanceolate, or obovate-oblong, margins crenate; silicles elliptic-rhomboid to orbicular rhomboid	36
–	Plants decumbent; leaves spathulate, cuneiform, linear-cuneiform, oblanceolate, narrowly ovate, to narrowly obovate (rarely orbicular), entire or margins sparingly, sometimes deeply toothed in upper ⅓; silicles broadly orbicular, orbicular (rarely ovate)	Lepidium oligodontum de Lange et Heenan1
36	Plants upright to spreading; basal leaf margins deeply toothed and/or lacerate for entire length	Lepidium panniforme de Lange et Heenan5
–	Plants decumbent to sprawling; basal leaf margins finely to sparingly deeply toothed, if deeply toothed then only in upper third of leaf	37
37	Leaves elliptic, elliptic-oblanceolate, obovate to elliptic-obovate, apex subacute, truncate to obtuse, upper third of leaf margins mostly crenate, or shallowly serrated; stamens 4; silicles 3.1–4.2 × 2.5–3.5 mm, elliptic-rhomboid to orbicular-rhomboid, not winged	Lepidium juvencum Heenan et de Lange
–	Leaves oblanceolate, cuneiform, oblong-obovate, obdeltoid to spathulate, apex praemorse margins finely to deeply incised in upper third or quarter, stamens 2–4; silicles 2.8–3.3 × 2.4–3.0 mm, orbicular, orbicular-ovate to ± rhomboid, margin winged	Lepidium oblitum Houliston, Heenan et de Lange6
38	Pedicels hairy	39
–	Pedicels glabrous	40
39	Inflorescence rachises glabrous (sometimes with sparse, pale, clavate hairs); pedicels hairy on adaxial surfaces only; petals 1.8–2.0 × 0.1–0.9 mm, elliptic or filiform (rarely obovate); plant of northern South Island	Lepidium banksii Kirk
–	Inflorescence rachises densely covered in white clavate hairs; pedicels densely and mostly circumferentially covered in white clavate hairs; petals 1.3–2.0 × 1.0–2.3 mm, obovate-spathulate (rarely orbicular); plant of Bounty Islands	Lepidium seditiosum de Lange, Heenan et J.Rolfe8
40	Plants with slender, upright stems; leaves thin, not fleshy, lanceolate, elliptic-lanceolate (rarely narrow elliptic), margin deeply serrate; silicles 4.0–4.7 × 3.2–3.5 mm, elliptic-rhomboid to orbicular-rhomboid, apex shallowly notched	Lepidium aegrum Heenan et de Lange
–	Plants with stout, upright to spreading short, rigid, stems; leaves thick and fleshy, broadly elliptic, elliptic-obovate to obovate-oblong, margin crenate; silicles 3.0–3.7 × 2.6–3.1 mm, orbicular to orbicular-rhomboid, apex obtuse to shallowly notched	Lepidium crassum Heenan et de Lange

¹ Lepidium oligodontum plants may have 2, 4 or 6 stamens, though 4 is the usual number. On occasion plants with mostly 2 stamens are known. For this reason this species may key out in three areas depending on the number of stamens present.

² We follow de Lange et al. (2009) and de Lange and Rolfe (2010) in treating Lepidium desvauxii as indigenous within the southern part of its New Zealand range (including the Chatham Islands), and naturalised within the more modified parts of central and northern New Zealand.

³ Lepidium ruderale is accepted by Webb et al. (1995) as naturalised in New Zealand.

⁴ Lepidium panniforme usually has 4 stamens but occasional plants with 2 or 2–4 stamens occur, and for this reason this species may key out in two areas depending on the number of stamens present.

⁵ Lepidium peregrinum is regarded here as naturalised to New Zealand (see Heenan and de Lange 2011). It is as an uncommon naturalised plant of glauconite and glauconitic limestone rock stacks and islands along the southern shore line of the Kawhia Harbour. Lepidium peregrinum is a threatened species in Australia (Scarlett 1999).

⁶ Lepidium oblitum may have 2–4 stamens. For this reason this species may key out in two areas depending on the number of stamens present.

⁷ Occasional plants of Lepidium naufragorum with simple or weakly pinnatifid leaves are also known, and these could be confused with Lepidium oleraceum from which they differ by the seasonal growth habit (with plants dying back to the rootstock over winter), and by the distinctly emarginate silicles

⁸ Lepidium seditiosum is known only from a single, imperfect gathering which lacks mature silicles. However, the shape of the ovary apex of immature silicles indicates that, in this species, they are notched.