Lunaria annua aka Honesty

Lunaria annua is known as honesty, money plant, and silver dollar. It belongs to the mustard family, Brassicaceae. Its native range covers south-central and southern Europe. It grows in temperate climates and is not native to Britain. Despite its name, this plant often lives for two years. The RHS also describes it as an annual. Plants grown from seed usually flower in their second year.

Honesty grows upright, with branches that give it a bushy shape. Garden plants reach about 2–3.3 feet [0.6–1 metre] tall. Their spread can reach 1–2 feet [0.3–0.6 metres]. The RHS gives a smaller spread of up to 1.6 feet [0.5 metres]. Growth is fast. The green stems may have a reddish tint and bear hairs. Green leaves grow along the stems in an alternate pattern. Each leaf is simple, with a pointed tip and toothed edge. Leaves range from broad oval to heart-shaped. Upper leaves have little or no stalk.

Purple flowers grow in loose racemes at the stem tips. NC State also records pink and white flowers. The blooms have a pleasant scent and four clawed petals. Flowering falls in late spring and early summer. Chicago Botanic Garden lists bloom months from March through June. Flat, round fruits develop by midsummer. These thin silicles turn translucent as they age. Their pale, pearly partitions give them a silver, coin-like look. The fruits provide much of the plant's garden value.

Grow honesty in fertile soil that stays moist but drains well. It accepts full sun or partial shade. The RHS lists chalk, loam, and sand as suitable soils. It also accepts acid, neutral, or alkaline soil. The RHS rates its cold hardiness H6. US sources give differing zone ranges: 4–8 and 5–9. Sow seed where plants will grow in early summer. Honesty suits borders, open woods, shade gardens, and informal beds. Its flowers attract butterflies, and its seedheads suit dried arrangements.

Honesty sheds seed freely and can become weedy. NC State reports it as invasive in some areas. Cut plants back after flowering when seed is not wanted. Leave seedheads in place when self-sowing is desired. Serious pest or disease trouble is uncommon, but problems can occur. The RHS lists club root and white blister. Missouri Botanical Garden also notes leaf spot and stem canker.