Blue Cohosh is a perennial herbaceous wildflower typically found in woodlands of oaks or maples where the native ground flora is still intact. Blue Cohosh is valued for its lacy, blue-green foliage and clusters of blue, fruit-like seeds. Leaves appear at mid-stem, blue in spring and turning bluish-green at maturity. Young plants are covered with a waxy bloom. Flowers give way in summer to attractive blue berry-like seeds (outer seed coating turns fleshy and blue as seeds mature) which resemble small grapes and provide ornamental interest into fall. The genus name comes from the Greek words kaulos meaning a stem and phyllon meaning a leaf. The species name recognizes that the foliage is similar to meadow rue ( Thalictrum ) . Blue Cohosh prefers dappled sunlight and shady woodland with average moisture and fertile, slightly acidic, loamy soil containing organic matter from decaying leaves and other plant materials. The soil should be consistently moist and not dry out. The large seeds are difficult to germinate and the plant is slow to spread on its own, but it can be divided just after flowering. However, once it becomes established at a favorable site, Blue Cohosh is long-lived and established plants are generally best left undisturbed. It can also spread very slowly by rhizomes to form colonies. Diseases, Insect Pests, and Other Plant Problems: No known diseases or insect pests.
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.
Dappled Sunlight (Shade through upper canopy all day) | Deep shade (Less than 2 hours to no direct sunlight) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
High Organic Matter; Loam (Silt); Sand
Soil pH
Acid (<6.0); Alkaline (>8.0); Neutral (6.0-8.0)
Soil drainage
Good Drainage | Moist
NC region
Mountains; Piedmont
Mature size
Height: 1 ft. 0 in. - 2 ft. 0 in. | Width: 0 ft. 6 in. - 1 ft. 0 in.
Growth rate
Slow
Maintenance
Medium
Canopy layer
4 - Herbaceous (1-3 ft)
Form & Appearance
Habit / form
Ascending; Erect
Foliage
Deciduous
Leaf color
Green
Leaf type
Compound (Pinnately , Bipinnately, Palmately)
Leaf arrangement
Alternate
Leaf shape
Oblong; Obovate; Ovate
Leaf margin
Entire
Leaf value
Showy
Leaf size
1-3 inches long, 1-3 inches wide
Hairs present
No
Leaf detail
On a flowering plant, a compound leaf is located at the middle of the central stem, where it is divided into a whorl of 3 compound leaflets. Each leaflet is divided into 9 simple subleaflets arranged in groups of 3. The subleaflets are 1 to 3 inches long and ¾ to 2 inches across, broadly ovate-oblong to obovate-oblong, and smooth along their margins. The surface of the subleaflets is glabrous and green. The upper compound leaf of a flowering plant is located under the inflorescence. This compound leaf resembles the lower compound leaf, except its 3 compound leaflets are smaller in size.
Flower color
Gold/Yellow; Green
Flower form
Panicle
Flower shape
Radial
Flower size
< 1 inch
Flower detail
On a flowering plant, the central stem terminates in a round floral panicle about 1 to 3 inches long; each panicle has 5 to 30 flowers. Individual flowers are about 1/3 of an inch across, consisting of 6 petaloid sepals, insignificant petals, 6 stamens, and an ovoid ovary with a beak-like style. Underneath each flower, there are 3 to 4 green bractlets that resemble sepals. The blooming period occurs in spring before the leaves have fully developed.
Bloom time
Spring
Fruit color
Blue; Gold/Yellow; Green
Fruit type
Berry
Fruit value
Showy
Fruit size
< 1 inch long, < 1 inch wide
Fruit detail
After flowering, berry-like seeds appear, 1/3 of an inch across. These seeds are initially green, but they later become bright blue at maturity during the summer. The seed coat is fleshy. Because of the bright blue seed coats, woodland birds disperse the seeds, which are known to be toxic to humans.
Stem color
Green; Purple/Lavender
Stem detail
Unbranched erect central stem is light green to pale purple, terete, glabrous, and often glaucous.
Wildlife & Ecology
Native status
Native
Origin
Central and Eastern Canada to North Central Eastern United State
Distribution
New Brunswick south to South Carolina, west to Arkansas and north to North Dakota and Manitoba.
Wildlife value
Pollen and nectar attract insects, foliage attracts caterpillars, and mice feed on the berries.
Low level toxin if eaten. Can result in vomiting and diarrhea. If eaten in excess, can cause high blood pressure and symptoms similar to nicotine poisoning.