How to Plant and Grow Cimicifuga

Cimicifuga takes center stage in late summer shade gardens when it debuts long candle-like spikes of airy white flowers in concert with its dark-green leaves. This plant—foliage plus flower spikes—reaches 4 to 6 feet tall and sometimes 8 feet tall in optimal conditions. The flower stalks, which are actually clusters of thin stamens, last more than three weeks.

Also called bugbane and black cohosh, cimicifuga is a long-lived woodland plant. Grow it with other woodland perennials, such as phlox, tall species of fern, astilbe, and angelica. Cimicifuga is especially eye-catching when it rises high above a hosta grouping. Cluster three to five cimicifuga plants together for an impressive show over a large area.

Where to Plant Cimicifuga

Cimicifuga is a shade garden plant. Grow it in a location with part shade or full shade where it is sheltered from strong winds and has room to expand. It's a slow grower but will eventually reach 4 to 6 feet tall and 4 feet wide. It grows best in humus-rich, moist soil and is an excellent addition to a shade garden bed, where it adds light and texture with its bright green foliage and sparkling white flowers. It also is an attractive specimen plant and can be grown outdoors in containers.

How and When to Plant Cimicifuga

Incorporate a large amount of well-decomposed compost or organic matter into the soil before planting cimicifuga.

Cimicifuga plants are frequently shipped as dormant bare-root rhizomes that are best planted in the fall. In prepared soil, dig a 6-inch-deep hole wide enough for the rhizome and the roots to spread out. Nestle the rhizome in the hole with the buds pointing up and the roots spread out underneath. Backfill with 3 inches of the prepared soil, tamp it down and add another 3 inches of soil. The rhizome should be just below the soil line. Space multiple roots 2 to 4 feet apart. Water the area once after planting, but winter rains or snow will be sufficient until spring.

Nursery-grown cimicifuga plants should be planted in spring. Dig a hole in prepared soil twice as wide as the nursery container and the same depth. Position the plant in the hole at the same depth as it was in the container and backfill the hole. Press down on the soil with your hands to eliminate air pockets. Water the plant.

Cimicifuga seeds can be sown directly into the garden in prepared soil, but they require a cold, wet stratification, so sow them in the fall. Sow four or five seeds for each plant on the surface of the soil and cover them lightly with compost. Keep the seeds moist until they germinate, which can take one month to a year.

Cimicifuga Care Tips

Cimicifuga is easy to care for when its basic requirements are met.

Light

Cimicifuga plants need part shade to full shade. In Zones 7 and warmer, full shade is essential; too much sun burns the plant's leaves and creates bedraggled-looking specimens.

If cimicifuga's leaf margins or whole leaves begin to turn brown, the plant is receiving too much sun or not enough water. If the plant is suffering from intense afternoon sun, move it to a lower-light location.

Soil and Water

Cimicifuga grows best in moist soil that is rich in organic matter. Incorporate compost annually until the soil develops the consistency of light, humusy woodland soil.

Don't let the plants dry out during the growing season. They need about 1 inch of water a week. Supplement natural rainfall when needed by watering regularly. Blanket the soil around cimicifuga plants with a 2-inch-thick layer of mulch to prevent soil moisture from evaporating.

Temperature and Humidity

Cimicifuga varieties prefer moderate temperatures. High heat slows the plants' growth. They also prefer moderate to high humidity rather than low humidity.

Fertilizer

Gardeners who add organic matter to the soil each spring don't need to supply additional fertilizer. Other gardeners should apply a balanced 10-10-10, slow-release granular fertilizer in spring, following the instructions on the product for the correct amount.

Pruning

Cimicifuga plants don't require much pruning. Deadhead the flowering tips when they die back and cut the plant down to the ground for winter.

Potting and Repotting Cimicifuga

Cimicifuga plants can enhance outdoor areas when grown in containers, although they are unlikely to survive the winter. Fill a container that has drainage holes with well-draining, organically rich garden soil. Plant a single tall cimicifuga in the center and add smaller plants around it to trail over the edges. Because plants in containers are more susceptible to cold temperatures than those in the ground, the plant probably won't survive winter in most zones unless it is brought inside to a sheltered place.

Pests and Problems

In general, cimicifuga species are relatively insect-free—it's no coincidence that one of the plant's names is bugbane. However, they are susceptible to leaf spot and other fungal diseases caused by soggy soil.

How to Propagate Cimicifuga

Cimicifuga can be propagated by division and seed.

Division: The simplest way to propagate cimicifuga in the garden is by dividing an existing plant. Dig up an existing plant in the fall, being careful not to damage the rhizomes. Separate it into two or three sections, each with healthy rhizomes. Replant the sections immediately in prepared soil. Water the plants well.

Seed: Propagating from seed is challenging because the seeds require cold stratification and the germination period is up to a year. Harvest seeds by removing the seed pods just as they begin to dry out; if you wait too long, the seeds will scatter. Put the seed pods in a paper bag for drying. When the pods are dry, separate the seeds from the pods by shaking the bag or crushing the pods with your fingers.

Sow the seeds in the fall in a prepared garden bed. Sprinkle four or five seeds for each plant on the soil surface and cover them lightly with compost. Keep the soil moist until the seeds germinate, which may take months.

Types of Cimicifuga

'Brunette' Cimicifuga

Actaea racemosa 'Brunette' has dark purple foliage that contrasts beautifully with white (and sometimes pink) flowers. Zones 3–8

'Atropurpurea' Cimicifuga

This variety of Actaea racemosa is the tallest of the purple leaf cultivars at 5 to 7 feet. Zones 3–8

Cimicifuga Companion Plants

Yellow Wax Bells

Yellow wax bells offer a stunning change of pace for fall gardens. The plant's dramatic dark stems are clothed with handsome 8-inch lobed leaves. From late summer into fall, nodding clusters of pale yellow, waxy bell flowers arise. Provide a sheltered position out of the wind where the soil is high in humus and retains moisture.

Hydrangea

Hydrangea, a shade-loving beauty, offers huge bouquets of clustered flowers, in various arrangements from mophead to lacecap, from summer through fall. Varieties of hydrangea differ in the size of plant and flower panicle, flower color, and blooming time. PeeGee hydrangeas grow into small trees; the flowers turn russet and cling into winter. Oakleaf hydrangeas have the most handsome foliage, which reddens dramatically in fall. Some newer hydrangeas feature huge flowers on compact plants, ideal for containers and small gardens. Hydrangeas thrive in moist, fertile, well-drained soil in partial to full shade. If you're seeking blue hydrangea flowers, check your soil's pH level and apply aluminum sulfate in spring to lower the pH to the 5.2–5.5 range. The change in hydrangea flower color results from lower pH and higher aluminum content in the soil.

Hosta

This plant, hardly grown 40 years ago, is now one of the most commonly grown garden plants. But hosta has earned its spot in the hearts of gardeners—it's among the easiest plants to grow, as long as you have some shade and ample rainfall. Hostas vary from tiny plants suitable for troughs or rock gardens to massive 4-foot clumps with heart-shape leaves almost 2 feet long that can be puckered, wavy-edged, white or green variegated, blue-gray, chartreuse, emerald-edged—the variations are virtually endless. Hostas in new sizes and touting new foliage features seem to appear each year. This tough, shade-loving perennial, also known as plantain lily, blooms with white or purplish lavender funnel-shape or flared flowers in summer. Some are intensely fragrant. Hostas are a favorite of slugs and deer.