Flora of New Zealand Series

Himalayan balsam

Annual, glabrous herb; stems erect, single but branched above, to c. 2.5 m high, succulent, ribbed, swollen at nodes. Petioles to c. 8 cm long, pink above, narrowly winged, with scattered purplish elongated glands in distal 1/2. Lvs opposite or in whorls of c. 3. Lamina 10-20 × 3-8 cm, lanceolate to ovate, sharply serrate; veins impressed above, raised below; base cuneate or attenuate; apex acuminate. Fls in diffuse cymes in upper lf axils of branches, shining. Bracts and lateral sepals 5-10 mm long, ovate, pink, acuminate. Posterior sepal forming large backwards projecting hood 2.2-3 cm long (excluding spur), pink or rose with dark spots inside; spur 5-7 mm long, rather stout, green. Corolla 2-lipped, white or pale pink; uppermost petal 1.5-2 cm long, subreniform; apex truncate to slightly emarginate; lateral petals very asymmetric, c. 3.5 cm long when stretched out, sharply bent in middle with lower halves forming a circular orifice enclosing the elongated anther mass. Anthers yellow. Capsule 2-3 cm long, usually purplish on exposed side, constricted in upper 1/2, with 5 acute ridges. Seed 3.5-5 mm long, ± broadly ovoid, shining black, with a single ridge down 1 side; base truncate; apex slightly beaked.

N.: most common in gullies and streams around Rotorua and Wellington; S.: Greymouth, Westport, S. Westland; St.: Halfmoon Bay.

Himalaya 1909

Wet areas along streams, roadsides and forest margins.

FL Nov-Mar.

Himalayan balsam is an escape from cultivation and also seeds freely inside gardens. In favourable conditions it grows very tall and may put out prop roots for anchorage. It has previously been known in N.Z. as I. roylei.