Aaron's Beard, or St. John's Wort, is a flowering deciduous herbaceous shrub or small tree, excellent for use on extreme slopes or sandy soils. Arron's Beard, like many in this family, spreads by underground stems and has moderate drought tolerance. It has 2 to 4 inch ovate or oblong, acute leaves and large 5-petaled, 5-sepaled yellow flowers with numerous, erect stamens that give a powder-puff appearance. It blooms in summer and, with its spreading habit, is often used as groundcover. The plant can grow in the heavy shade of trees and in dry shade and is vigorous to the point where it can swamp out small plants. To maximize its use as a ground cover, you can cut it to ground level in the spring. It can be considered an evergreen in warm winter climates, but usually dies to the ground in cold winters. However, it blooms on new growth and comes back each spring. Aaron's Beard prefers fertile, loamy well-drained acidic soil, but it is easily grown in any well-drained but moisture retentive soil including dry soils and heavy clay. It will grow in sun or shade, but flowers best in a sunny position. It tolerates cold and drought once established and is ornamental but rapidly spreading by means of stolons. Diseases, Insect Pests, and Other Plant Problems: No significant problems. Rust can sometimes be a problem.
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.
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
Clay; Loam (Silt); Sand
Soil pH
Acid (<6.0)
Soil drainage
Good Drainage | Moist | Occasionally Dry
Available space
12 inches-3 feet
Mature size
Height: 1 ft. 0 in. - 1 ft. 6 in. | Width: 1 ft. 6 in. - 2 ft. 0 in.
Growth rate
Rapid
Maintenance
Low
Canopy layer
4 - Herbaceous (1-3 ft)
Form & Appearance
Habit / form
Horizontal; Spreading
Texture
Medium
Foliage
Broadleaf Evergreen; Deciduous
Leaf color
Blue; Green; Purple/Lavender
Leaf type
Simple
Leaf arrangement
Opposite; Whorled
Leaf shape
Oblong; Ovate
Leaf margin
Entire
Leaf size
3-6 inches long
Hairs present
No
Leaf detail
Three to four inch long medium to dark green leaves; bluish green below; purplish in the fall. Opposite or whorled, decussate, simple, entire; sessile or petiole short.
Fall color
Purple/Lavender
Flower color
Gold/Yellow
Flower value
Showy
Flower form
Cyme
Flower shape
Cup; Star
Flower size
1-3 inches
Flower detail
Single 3 inch yellow flowers. Solitary or cymose, terminal or axillary. Yellow (usually) 5-petaled (rarely 4), 5 sepals (rarely 4); stamens numerous, in bundles or in showy boss. Flowers appear singly or in groups of 2 or 3 and cover the plant in summer.
Bloom time
Summer
Fruit type
Capsule
Fruit detail
Three to five celled capsule, sometimes fleshy.
Stem detail
Contain 2 to 4 (up to 6) ridges on newer growth, smooth and rounded on older growth. Four-angled stems are both procumbent and ascending.
Wildlife & Ecology
Native status
Non-native
Origin
Southern Europe, Western Asia, Turkey
Distribution
West Coast of the United States, introduced into Tennessee and North Carolina.