Stirp. Austr. Fasc. ed. 2, 2: 352. 1769.
Annuals. Stems erect to ascending, (8–) 10–20 (–40) cm, glandular and eglandular-hairy. Leaves: blade lanceolate to ovate, 7–19 (–21) × (3–) 5–12 mm, 1–2 times as long as wide, base cuneate, margins (proximal) crenate-dentate or (distal) ±palmatifid, lobes 3–7+, apex of central lobe obtuse, lateral ± acute, surfaces glandular and eglandular-hairy. Racemes 1, terminal, 60–180 mm, 15–50 (–120) -flowered, axis eglandular and glandular-hairy; proximal bracts similar to leaves, distal ones linear-lanceolate, 3–5 mm. Pedicels erect, 2–4 (–5) mm, shorter than subtending bract, length 1/2–1 times calyx, eglandular and glandular-hairy. Flowers: calyx lobes 3.5–6 mm, apex acute, eglandular and glandular-hairy; corolla deep blue, 4–6 mm diam.; stamens 0.8–1.5 mm; style 0.8–1.5 mm, stigma violet. Capsules compressed in cross-section, narrowly obcordiform, 3.5–4.5 × 4–6 mm, apex emarginate, angle of sinus ca. 90°, ciliate with glandular and eglandular hairs. Seeds 10–28, yellowish, ellipsoid, flat, 0.9–1.6 × 0.7–1.3 mm, 0.2–0.3 mm thick, smooth. 2n = 16 (Eurasia).
Phenology: Flowering (Mar–)Apr–Jul.
Habitat: Open pine and oak forests, rocky, dry, sandy slopes.
Elevation: 500–2200 m.
Introduced; Ill., Ind., Mich., N.Y., Va., Wis., Eurasia
Veronica dillenii is closely related to V. verna but with larger flowers; it may have been overlooked and may be distributed more widely. Most herbarium specimens of V. dillenii blacken when dry due to the presence of aucubin, which distinguishes them from V. verna.