Meadow rue, related to columbine and delphinium, has sprays of summertime flowers above airy, fine-textured foliage. Instead of true petals, the flowers have petal-like sepals and stamens in shades of pink, purple, white, and yellow. Taller species thrive in woodland and back-of-border settings, and shorter varieties prefer moist, shady rock gardens.
- Common name: Meadow rue
- Botanical name: Thalictrum spp.
- Zones: 4 to 9, depending on species
- Size: To 10 feet tall, depending on species
- From: Areas of Europe, Asia, and North America
- Family: Ranunculaceae (ranunculus family)
- Sun: Partial shade.
- Soil: Moist, well drained, slightly acidic soil that's rich in organic matter.
- Moisture: Water during times of drought.
- Mulch: Lay a 2- to 3-inch layer of mulch over the soil around the plants. Use winter mulch only after the soil has frozen.
- Pruning: Cut plants back in autumn after freezing temperatures arrive or in spring before plants begin to grow.
- Fertilizer: Fertilizer is generally not necessary in soils that are rich in organic matter. If desired, use a balanced fertilizer in spring.
- Staking: Taller types may need staking when in bloom. To avoid harming the root system, sink a tall stick into the ground a short distance from the plant. Use a figure-eight pattern to tie the plant, with the stem in one loop and the stake in the other. This helps prevent excessive rubbing, which can leave a wound and allow diseases to enter the plant.
- Seed: Sow seeds in a cold frame or sheltered spot in autumn.
- Division: Divide anytime the soil isn't frozen. Spring and autumn are best.
- Aphids: These small insects often appear in large numbers on new growth. Spray them daily with a stream of water; they will not attack a plant after being knocked off. Use an insecticidal soap or neem-oil-based spray for severe infestations.
- Leaf spot: In summer or autumn, leaves develop yellow or dark spots that often have concentric rings, forming a bull's-eye pattern. To deter it, prune the plant to maintain good airflow, and avoid wetting foliage in afternoons and evenings.
- Powdery mildew: This disease appears in mid- to late summer. Affected leaves develop a gray powdery covering and fall off the plant. To deter the disease, prune the plant to maintain good airflow, and avoid wetting foliage in afternoons and evenings.
- Slugs and snails: Slugs and snails tend to chew leaves at night. To deter them, surround plants with a ring of horticultural grade diatomaceous earth. Some gardeners lay copper strips around plants, but this isn't always successful. If slugs aren't particularly numerous, set out shallow containers of stale beer at ground level. Slugs, attracted to the beer, crawl into it and drown.
- Thalictrum actaeifolium: Grows to 3 feet tall with blue-green foliage. Pink flowers in summer. Zones 4 to 9.
- Thalictrum aquilegiifolium: Grows to 4 feet tall with blue-green foliage with a powdery coating. The foliage is similar to columbines. Clustered purple flowers in summer. Zones 5 to 9.
- Thalictrum aquilegiifolium ‘Thundercloud': Grows to 4 feet tall with blue-green foliage. Purple flowers in summer. Zones 5 to 9.
- Thalictrum delavayi: Grows to 4 feet tall with blue-green foliage. Lavender flowers in summer. Zones 5 to 9.
- Thalictrum diffusiflorum: A species with especially large flowers that resemble clematis. The foliage has a fine texture and the plants grow to 2 feet tall. Zones 5 to 9.
- Thalictrum ‘Elin': Has steel blue foliage that resembles columbine leaves. Lavender-and-yellow flowers in summer. Grows 10 feet tall. Zones 5 to 9.
- Thalictrum flavum subsp. glaucum: Grows to 5 feet tall with dusty, blue-green foliage. Yellow flowers in summer. Zones 5 to 9.
- Thalictrum ichangense: Grows to 1 foot with pinkish flowers and metallic green foliage. Zones 6 to 9.
- Thalictrum ‘Illuminator': Has blue-green foliage that turns chartreuse as the season progresses. Yellow flowers in summer. Grows 5 feet tall. Zones 5 to 9.
- Thalictrum kiusianum: Dwarf species that grows 6 inches tall. The foliage resembles a maidenhair fern; summertime flowers are purple. Zones 4 to 8.
- Thalictrum rochebruneanum: Grows to 5 feet tall with reddish pink flowers. Zones 5 to 9.