Aristolochia clematitis aka Birthwort

Aristolochia clematitis is also known as birthwort. It belongs to the birthwort family. Its native range runs from Europe to the Caucasus. It grows in temperate regions but is not native to Britain. Records show it in gardens, orchards, and waste ground. This plant lives for more than one year. It spreads through rhizomes, which are stems beneath the soil. These stems creep and branch. Unlike many related plants, it does not form a climbing vine.

Garden plants reach 2–3 feet [0.6–0.9 metres] tall. Some reach 4 feet [1.2 metres]. Reports give a garden spread of 1.6–3 feet [0.5–0.9 metres]. The stems stand upright, though some may lean or scramble. Heart-shaped leaves grow along them. The leaves reach 4.5 inches long. They range from mid green to dark green. Sources differ on whether the leaves last through winter. Missouri Botanical Garden calls it deciduous, meaning it sheds its leaves. RHS lists it as evergreen, meaning it keeps its leaves.

Flowers appear from late spring into midsummer. Missouri Botanical Garden gives June–July as the bloom time. Flowers grow in groups where leaves meet the stems. They may be pale yellow, greenish yellow, or yellowish brown. Each has a narrow tube. Its upper lip curves and ends in a point. The flowers have no petals. Tiny insects pollinate them. The plant also draws butterflies. The leaves give it much of its garden value. Small groups suit borders and beds. They also suit sites where plants can spread on their own.

Birthwort grows in full sun or part shade. Some shade helps where summers are hot. It needs rich soil that drains well, with moderate moisture. Avoid dry soil while it grows. RHS favours drier soil in winter. It accepts sandy, loamy, or chalky soil across a broad pH range. Missouri Botanical Garden gives USDA zones 6–9. Zone 5 may also suit it. RHS rates it H6 for UK conditions. Growers can raise plants from seed or root cuttings. They can also split plants to grow more.

It needs little routine care, but strong growth can cause unwanted spread. Serious pests and diseases are rare. Root rot, leaf spot, and southern blight may occur. RHS also notes possible honey fungus. Whether the plant is prone to it remains unclear. Birthwort has no known food use and is poisonous. Its roots and stems contain aristolochic acid. This substance can harm kidneys and cause cancer. Past use as medicine does not make it safe to take. RHS warns that eating it harms people and dogs. RHS also advises gloves and protective gear when handling plants.