Sinapis alba L.
white mustard
Annual taprooted herb. Stem erect, branching, bearing stiff reflexed hairs especially near base, or sometimes glabrous, 60-100 cm tall. Lvs glabrous or sparsely covered in coarse hairs, toothed. Lower lvs lyrate-pinnate, rarely 2-pinnatifid, 10-20 × 5-10 cm; terminal leaflet broadly ovate to triangular, shallowly to deeply 3-lobed, wider than rest of lf; lateral leaflets alternate, oblong to ovate, in (0)-1-4 pairs, the proximal ones usually shallowly toothed but rarely entire. Upper lvs petiolate, similar to lower but smaller, sometimes simple and 3-lobed. Racemes erect, to 40 cm long, glabrous or with sparse reflexed hairs. Pedicels patent to reflexed at fruiting, 10-20 mm long. Sepals ovate to obovate, glabrous, 3-6 × 1-1.5-(2) mm. Petals 7-11 × 3-5 mm. Silique (1)-3-6-(8)-seeded, ± constricted between the seeds, bearing bristly hairs especially on veins, rarely glabrous, 15-30 × 2-5 mm; beak strongly flattened, 0-1-seeded, = or > valves.
N.; S.: occasional throughout.
Europe, Middle East, N. Africa 1883
Casual weed of agriculture, gardens and waste land.
Most N.Z. material can be referred to subsp. alba, but one collection, a weed in linen flax in Southland, is subsp. dissecta (Lagasca) Bonnier (sometimes accorded sp. rank as S. dissecta Lagasca). The above description includes both subspp.; subsp. dissecta differs by its 2-pinnatifid lvs and glabrous, weakly veined siliques. This sp. has also been referred to in N.Z. as Brassica alba.
