Lepidium peregrinum
Common name
wandering pepper cress
Family
Brassicaceae
Flora category
Vascular – Exotic
Structural class
Herbs - Dicotyledons other than Composites
Conservation status
Not applicable
Distribution
Naturalised. New Zealand, North Island, Kawhia Harbour , O wiwi ku Island. Indigenous to eastern Australia.
Habitat
In New Zealand known from small rock stacks and an island located near the southern shore line of the Kawhia Harbour, where it grows amongst rank grasses and herbs (including Rorippa divaricata) overlying glauconite and glauconitic limestone. In Australia known only from a few sites in southern Queensland and northern New South Wales (Scarlett 1999).
Detailed description
Perennial herb to sub-shrub, usually 0.1–0.8 m tall, sometimes ascending to 2 m in surrounding vegetation. Stems erect to decumbent, slightly angular and ridged, glabrous or rarely sparsely vestured with blunt peg-like hairs. Rosette and lower cauline leaves variably petiolate, the lamina pinnatifid with a large broad-lanceolate terminal lobe, vestured with long-acicular hairs on the upper surface and margins, the distal margins serrate (60–100 mm long, 15–25 mm wide). Mid-cauline leaves lanceolate and broadly petiolate, the serrate to serrulate margins with numerous tooth-like hairs; branch-subtending leaves with auriculate to sagittate bases at the point of leaf insertion, sessile to subsessile (40–90 × 4–9 mm). Upper cauline leaves narrow-lanceolate to linear, often with entire margins with sparse tooth-like hairs, the bases usually attenuate at the point of leaf insertion (10–20 × 1.0–1.5 mm). Inflorescences initially corymbose, elongating during flowering to a maximum of 200 mm. Branch-terminal racemes often appearing lateral and leaf-opposed, overtopped by a subtending axillary flowering branch. Rhachis glabrous to minutely puberulent towards the apex, slightly angular and ridged. Flowers minute; sepals 0.5–0.75 mm long, the adaxial sepal dorsally villous in the upper half, the abaxial sepal glabrous or with 1 or 2 hairs, the lateral pair of sepals always glabrous. Petals reduced or absent. Stamens 2, median. Pedicels 3–5 mm long at maturity, erecto-patent to sub-declinate and usually arcuate at fruiting, slender and subterete with a slightly flattened puberulent adaxial surface, 1.3–2× as long as the silicles. Silicles ovate to elliptical 2.0–3.0 × 1.5–2.0 mm, acutely emarginate with triangular wings forming a V-shaped notch. Styles short, included in the notch. Valves green or purple, glabrous. Seeds narrowly ovoid, 1.25–1.5 × 0.5–0.75 mm, wingless. Cotyledons incumbent. Description modified from Scarlett (1999).
Similar taxa
Lepidium pseudotasmanicum is superficially similar to L. peregrinum. This common weedy species is easily distinguished from L. peregrinum by the mid-cauline leaves which are oblanceolate to cuneate (lanceolate in L. peregrinum); and by the leaf margins which are acutely dentate and usual with spreading apical lobes margins, and these often reduced to a single terminal pair ( margins serrate/serrulate and without apical lobes in L. peregrinum). In L. peregrinum the lower cauline leaves are lyrate-pinnatifid with serrated margins and with a large terminal lobe. Those of L. pseudotasmanicum are pinnatifid with the terminal margins of the linear lobes often deeply dentate (not serrate)
Flowering
January-August
Fruiting
February-April
Propagation technique
Limited New Zealand material is in cultivation. Seed germinates readily and plants are quick growing but like all other lepidia are prone to insect attack and fungal diseases. Does best in a soil rich in N, P, K and free draining but moist soil. Should be grown in full sun in an open place.
Threats
Unknown. This species was only discovered in New Zealand in January 2010 by accident, though its presence in this country was suggested by N. Scarlett to P.J. de Lange in 2007, as it is very easily confused with L. pseudotasmanicum. So far the only known populations are on a small island which is rarely visited and free from browsing animals. The biostatus of the species has recently been researched by P.J. de Lange & P.B. Heenan and they conclude that Lepidium peregrinum is naturalised rather than indigenous to New Zealand. The species is threatened in Australia.
Year naturalised
2010
Origin
Australia, either side of the border between New South Wales and Queensland
Etymology
lepidium: Scale-shaped (pods)
References
Scarlett, N.N. 1999: The identity of Lepidium peregrinum (Brassicaceae), an endangered Australian plant species. Telopea 8: 337-350.
Fact Sheet Prepared for NZPCN by: P.J. de Lange November 2010. Modified from Scarlett (1999) which is based on Australian specimens.