Bupleurum rotundifolium aka Thoroughwax

Bupleurum rotundifolium is an annual in the carrot family, Apiaceae. Common names include hare's ear, thorow-wax, and thoroughwort. Its native range spans Europe, the Mediterranean, and Central Asia. It also grows in parts of North America. It occurs in crop fields, waste ground, and roadsides. Once a cornfield weed, it now has garden uses. The RHS notes that wild plants have become scarce.

Plants grow upright and branch from reddish stems. Garden heights range from about 1–2 feet [0.3–0.6 metres]. The RHS describes shorter plants reaching 1 foot [0.3 metres]. Spread can reach about 1.6 feet [0.5 metres]. This fast-growing plant reaches full size within one year. Its blue-green leaves lack hairs and alternate along the stem. Lower leaves range from oval to oblong. The upper leaves are rounder and have many veins. They surround the stem, which seems to pass through them. This leaf form explains the old name thorough-wax.

Small yellow to greenish flowers form umbels at branch tips. Rings of leaf-like bracteoles sit beneath the flower clusters. These bracteoles have clear veins and pointed tips. Flowering runs from summer into fall. The blooms last well in cut arrangements. They also suit dried flower work. Tiny, oblong fruits turn black as they ripen. They remain closed at maturity and appear in summer and fall.

Grow this species in full sun and soil that drains well. NC State also reports that it accepts partial shade. It grows in sandy, loamy, or chalky ground. Acid, neutral, and alkaline soils all suit it. Soil moisture can range from dry to moist. The RHS gives a UK hardiness rating of H5. NC State lists USDA zones 5–9. Sow fresh seed in autumn, or use a cold frame in spring. Plants can seed themselves; remove spent flowers to limit spread.

Hare's ear suits borders, small spaces, and cutting gardens. It also fits gravel gardens, meadows, and informal planting. Its foliage and greenish blooms contrast with brighter flowers. Care needs are low, with few reported pest or disease problems. It can become weedy where it seeds freely. The leaves are edible, either raw or cooked. PFAF records their use in salads, cooked greens, and seasoning. It lists no known hazards, but gives no pet-safety guidance. NC State records medicinal use; PFAF lists no known medicinal uses.