Veronica dieffenbachii Benth.

Spreading and low to erect shrub to 3 m tall. Stems spreading to erect, or pendent on cliffs, eglandular-pubescent or sometimes glabrous; hairs bifarious or uniform. Leaf bud distinct, its leaves appressed at margins until fully grown; sinus absent. Leaves opposite-decussate or sub-distichous, erecto-patent to recurved; lamina coriaceous, elliptic, oblong-elliptic, obovate, or oblanceolate, 26–102 mm long, 4.5–25.0 mm wide, dull, pale to dark green above, pale green to glaucescent beneath; midrib evident; surfaces eglandular-hairy all over or along midrib above, minutely glandular-hairy or sometimes glabrous or rarely eglandular-hairy beneath; margin glabrous or rarely sparsely ciliate, entire; apex sub-acute or acute; base truncate, sub-cordate, or amplexicaul; petiole absent. Inflorescence a lateral raceme, 50–115 mm long; flowers crowded, 34–135, all bisexual; bracts alternate or loosely whorled, linear-lanceolate to deltoid, usually <, rarely about =, pedicels; pedicels erecto-patent to spreading, 0.7–3.8 mm long, eglandular-puberulent all around, sometimes with minute glandular hairs as well. Calyx lobes usually 4, rarely 5 (5^th lobe small, posterior), sub-acute to acuminate, 1.5–2.0 mm long, unequal, glabrous or eglandular-hairy on surfaces, mixed glandular- and eglandular-ciliate on margins. Corolla 5.5–7.0 mm diameter; tube white, 2.5–3.5 mm long, > calyx, eglandular-hairy inside and on bases of lobes; lobes 4, white or pale purplish fading white, spreading to recurved, sub-equal, elliptic to ovate, 2.5–3.5 mm long, obtuse to rounded; nectar guides absent. Stamen filaments white or pale purplish, 3.5–4.0 mm long; anthers magenta. Style glabrous or eglandular-hairy, 4.0–7.5 mm long. Capsules latiseptate, sub-acute to obtuse, glabrous or sometimes eglandular-hairy, 3.5–5.6 mm long, 2.7–4.3 mm at widest point. Seeds discoid, flattened, smooth, pale brown to brown, 0.8–1.5 mm long.

Of the woody veronicas on the Chatham Is., V. barkeri plants are distinguished from V. dieffenbachii by usually being trees, having greener leaves, broadest below or towards the middle, usually with ciliate margins and dense stomata beneath, and the corolla tube < calyx. V. chathamica plants are usually smaller, with smaller, more rounded leaves that are cuneate at the base, inflorescence rachis and pedicel hairs longer (0.10–0.25 mm), and long narrow bracts ≥ pedicels.

Rock outcrops and scrub, mostly near the coast or lagoon shores. Recorded elevations range from 0 to 240 m.

It is possible that V. dieffenbachii hybridises with V. chathamica, because some specimens combine features of both species, such as longer bracts and longer inflorescence hairs than are usually found in V. dieffenbachii.

Flowers: December–February, extending to March; fruits January–April, persisting all year.

2n = 40 (see Bayly & Kellow 2006, as Hebe dieffenbachii).

Veronica dieffenbachii is classified in V. subg. Pseudoveronica sect. Hebe and the informal group “Occlusae” (Albach & Meudt 2010; Bayly & Kellow 2006).

V. dieffenbachii is variable in some characters (e.g., leaf size and shape, stem pubescence, inflorescence pubescence, and bract length and shape).

Some plants of V. dieffenbachii and V. chathamica have been observed with blue or purple pollen, but it is more often whitish.