Aaron's Beard or St. Johnswort

(Hypericaceae - St. Johnswort Family)

Form

• medium-sized, semi-evergreen, semi-woody perennial groundcover
• maturing at 1' high by 2' long
• procumbent mat growth habit
• medium growth rate (in terms of its peripheral spread)

Culture

• full sun to full shade
• prefers moist, well-drained, average fertility soils in partial shade, but is tolerant of poor soils, sandy soils, various soil pHs, some soil compaction, heat, and drought
• propagated by rooted stem cuttings, crown division, or separation and replanting of the peripheral underground stolons
• St. Johnswort Family, with virtually no disease or pest problems
• low availability, in containers or flats
• in Northern climates, shear or mow the previous season's winterkilled or winterburned growth to the ground every late Winter to allow new growth to arise unimpeded
• in Southern climates, mow as noted above after harsh Winters, or mow every third year to rejuvenate the groundcover
• mulch lightly to control weeds during transplant establishment

Foliage

• emerges chartreuse-bronzed, but quickly turns to medium green then dark green, with fall color being a deep blue-green
• opposite, oval to elliptical, very attractive and honeysuckle-like, about 3" long, with a very short petiole
• foliage is semi-evergreen (but winterburned) or dead cinnamon brown by the end of most Northern winters (evergreen in Southern climates)

Flowers

• bright canary yellow, predominately in June and July and sporadically through September atop the new growth
• the scattered yellow flowers are a stunning natural contrast against the medium- to dark-green foliage background, with each flower effective for one to two weeks
• the 2" wide solitary flowers have 5 yellow petals that are somewhat spreading to recurved, exposing the 1" tall abundant central yellow filaments

Fruits

• sparse and ornamentally insignificant

Twigs

• green on the current season's growth, becoming brown with Winter dieback

Trunk

• not applicable

ID Summary

• opposite leaves emerge chartreuse-bronzed but quickly turn to medium green, dark green, then blue-green, densely covering the procumbent stems, with bright yellow solitary flowers blooming in mid-Summer
• foliage is semi-evergreen to ever-brown in Northern climates, but evergreen in Southern climates

USAGE

Function

• semi-evergreen groundcover for foundations, mass plantings, and embankments

Texture

• medium texture
• thick density

Assets

• showy yellow flowers in mid-Summer
• excellent, clean dense foliage on short stems
• moderately urban tolerant
• dense coverage, but not invasive

Liabilities

• must shear back or mow to the ground every late Winter or early Spring in Northern climates due to Winter dieback of the stems

Habitat

• zones 4 to 8
• native to Southeastern Europe and Asia Minor

SELECTIONS

Alternates

• good but little-utilized dense groundcovers (Convallaria majalis, Galium odoratum, Liriope spicata, Sedum sarmentosum, Waldsteinia, etc.)
• Summer-flowering groundcovers (Coronilla varia, Hemerocallis 'Eenie Weenie', Liriope muscari, etc.)
• moderately urban-tolerant groundcovers (Ajuga reptans, Euonymus fortunei 'Colorata', Hedera helix, Juniperus conferta, etc.)

Variants

• the species form is the only form commercially available
• related species or hybrids are usually small shrubs or tall groundcovers with bright yellow flowers

NOTES

Translation

• Hypericum translates as "above a picture", referring to the fact that in ancient cultures, cuttings from members of the genus were hung above pictures to ward off evil spirits.
• calycinum translates as "with a conspicuous calyx", referring to the portion of the corolla structure that lies beneath the yellow petals.

Purpose

• Aaron's Beard is a groundcover noted for its lush dark green to bluish-green foliage and its yellow flowers in Summer.

Summary

• Hypericum calycinum is a perennial groundcover having scattered but attractive yellow flowers during Summer, contrasting against a dark green background of dense foliage arranged along procumbent stems.