Saponaria officinalis aka Sweet Betty

Saponaria officinalis is a perennial herb known as soapwort or bouncing bet. It belongs to the pink family, Caryophyllaceae. Its native range runs from Europe to the Caucasus. It has spread beyond gardens across much of North America. Wild plants grow in fields, beside streams, and along roads. They also grow on waste ground and beside railway tracks.

Soapwort forms clumps and spreads through underground stems called rhizomes. Garden plants stand about 1–3.3 feet [0.3–1 metre] tall. North Carolina State lists a lower upper height of 2.5 feet [0.76 metre]. Clumps reach about 1–1.6 feet [0.3–0.5 metre] wide. The upright stems are smooth and green, sometimes with red tints. Green leaves grow in pairs on opposite sides of each stem. They range from broad lance shapes to oval shapes. Each leaf has smooth edges and three to five main ribs. The plant loses its leaves for winter.

Small flower clusters form at the tips of the stems. The blooms are pink or white and have a scent. Each flower spans about an inch and has five notched petals. A narrow, tube-shaped calyx sits behind the petals. It ranges from pale green to reddish and ends in five teeth. Bloom dates vary among the sources. Chicago Botanic Garden lists May to June. Other accounts place flowering in summer, with RHS extending it into autumn. The fruit is a capsule. Flowers draw butterflies, moths, and hummingbirds to the garden.

Grow soapwort in full sun and soil that drains well. It suits neutral to alkaline soil and tolerates poor ground. Sources list sand, chalk, clay, and shallow rocky soils. It accepts dry to moist conditions and withstands drought. Chicago lists USDA zones 3–9; North Carolina State lists zones 2–8. RHS rates it H7 for cold hardiness. Use it in borders, cottage gardens, meadows, or as ground cover. It tolerates light foot traffic and resists deer. Its strong spread can make it a garden weed. Slugs and snails may attack it, but diseases cause few problems.

Saponins in the plant produce lather when mixed with water. The plant and roots have served as cleaners for fine fabrics. Soapwort also has a history of use for coughs and itchy skin. These uses do not make it safe to eat. No edible uses are recorded. Roots and seeds can cause nausea, vomiting, and diarrhoea. Plant-based washes may irritate the eyes.