Thalictrum dioicum aka Early Meadow Rue

Thalictrum dioicum is also known as early meadow rue. It belongs to the buttercup family. This perennial lives for more than one year. It grows in eastern and central North America, including southeastern Canada. Wild plants grow in moist woods and places where water seeps. In Missouri, they also grow on wooded slopes and in ravines. Some grow on ledges near exposed limestone. It blooms as trees start to leaf out in spring.

Plants form upright, open clumps with fine leaves. Most garden plants reach 1–2 feet [0.3–0.61 metres] tall and wide. RHS gives a wider range, reaching 3.3 feet [1 metre]. The compound leaves have several lobed parts. Their color ranges from gray-green to blue-green. They can look like columbine or maidenhair fern leaves. The smooth, round stems range from pale green to purple-green. The leaves die back, often by midsummer in hot weather. Low leaves grow at the base again in fall.

Small flowers hang in loose, branched groups called panicles. They bloom from April to May. Some garden records list blooms from spring into summer. The flowers lack petals but have green sepals. They look greenish white, at times with purple edges or tints. Male and female flowers grow on separate plants. Male flowers have yellow stamens, the parts that bear pollen. Female flowers have purple pistils, the female flower parts. Wind moves pollen from plant to plant. Female flowers form small dry fruits called achenes. These ripen in summer and have strong ribs and pointed ends.

Grow this plant in moist soil that drains well. It prefers rich soil with humus and patches of sunlight. It also grows in full sun or partial shade. Sources list several soil textures and all main pH ranges. Heat and humid weather can cause problems. Its listed hardiness spans USDA zones 4–7 and RHS H4. It grows at a moderate rate. Mature clumps may need support. Choose a sheltered site to limit harm from strong winds. Divide plants in spring when new growth starts.

Early meadow rue suits borders, woodland gardens, and meadows. It also suits areas where plants can spread on their own. Its leaves set off perennials that bloom later. The flowers suit cutting, and deer tend to avoid it. Chicago Botanic Garden lists it as of interest to birds and butterflies. Serious pests and diseases seldom cause problems. Slugs may attack it. Rust and powdery mildew sometimes occur. Dry weather can favor mildew. Remove old flower stems in autumn or before spring growth. This also limits new plants from unwanted seed spread.