Phuopsis stylosa aka Crosswort

Phuopsis stylosa is a low, spreading plant in the Rubiaceae family. Gardeners know it as Caucasian crosswort or creeping crosswort. Its native range runs from the Caucasus to northwestern Iran. It grows on hillsides and in woods with deciduous trees. It forms a leafy mat and grows fast. Garden sources treat it as a herbaceous perennial. Kew classes its life form as a subshrub.

Plants reach about 0.5–0.75 feet [0.15–0.23 metres] in garden beds. They spread about 1–2 feet [0.30–0.61 metres] wide. RHS gives a broader height range, reaching 1.6 feet [0.5 metres]. The narrow, pointed leaves grow in whorls around square stems. Each whorl holds six to nine bright green leaves. Fine, stiff hairs line their edges, and the foliage has scent. RHS describes the foliage as semi-evergreen, though its summary calls it deciduous.

Small pink flowers form round clusters at the stem tips. Each flower has a narrow tube. The clusters reach about 0.125 feet [0.038 metres] across. Their shape gives them the look of small pincushions. Missouri Botanical Garden lists bloom from June through August. Its description also notes flowers from late spring into early summer. The flowers have scent and draw butterflies to the garden.

Grow this plant in sun or partial shade. It needs soil that drains well and stays moist. It also grows in poor soil. Established plants withstand dry soil and spells of drought. Cool summers suit it best. Deep South heat and humidity can cause plants to fail. RHS lists sand, loam, and chalk as suitable soils. It accepts acidic, neutral, and alkaline conditions. Its hardiness ratings are USDA zones 5–8 and RHS H5. Plants may take two to five years to mature.

Use it along border edges, on slopes, or in rock gardens. Its stems can trail over walls or container edges. It also serves as ground cover on difficult sites. Deer and rabbits tend to leave it alone. Both garden sources report few pest or disease problems. It can seed itself around the garden. Remove faded flowers to limit unwanted seedlings. Cut plants back after bloom to keep growth compact. Raise new plants from seed, spring divisions, or summer cuttings.