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Lamiastrum galeobdolon (yellow archangel)
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© Jan Færk, some rights reserved (CC-BY) · GBIF
Perennials

Lamiastrum galeobdolon

yellow archangel

Lamiaceae
Europe and western Asia; naturalized in the Pacific Northwest (southern British Columbia through western Washington and Oregon to northern California)

At a Glance

TypePerennial
HabitSpreading
FoliageEvergreen
Height8-24 inches (20-60 cm)
Width24-72 inches (60-180 cm) and spreading indefinitely by stolons
Maturity2 years

Growing Zones

USDA Hardiness Zones

4 - 9
Zone 4Zone 5Zone 6Zone 7Zone 8Zone 9
These zones indicate the coldest temperatures this plant can typically survive.
What's my zone? →
Frost Tolerancehardy

Key Features

Attracts PollinatorsDeer Resistant
Maintenancehigh

Overview

Lamiastrum galeobdolon (synonym Lamium galeobdolon) is a stoloniferous evergreen perennial ground cover in the mint family (Lamiaceae) reaching 8–24 inches (20–60 cm) tall and spreading 2–6 feet (0.6–1.8 m) wide per year via long above-ground stolons. Stems are square in cross-section — the Lamiaceae diagnostic. Leaves are opposite, ovate to triangular, 1–3 inches (2.5–8 cm) long, with crenate-serrate margins. The cultivated form most commonly escaped in the Pacific Northwest is the variegated cultivar (sold as L. galeobdolon 'Hermann's Pride' or 'Variegatum'), with dark green leaves bearing conspicuous silvery-white splotches that carry year-round identification value. Flowers are yellow, two-lipped, 0.6–0.8 inch (15–20 mm) long, with brown markings on the lower lip, borne in whorls of 4–8 in the upper leaf axils in late spring. Stolons run long and arching, rooting at the nodes, extending 3–6 feet (0.9–1.8 m) per year under favorable conditions. Stolon fragments as short as 2 inches (5 cm) with a single node regenerate into new plants, making fragment-driven spread the principal mechanism by which the species invades beyond cultivated positions. Dense mat-forming colonies smother native ground cover in forest understory positions and reduce native-plant diversity by 60–80% across invaded patches within 3–5 years of establishment. Listed as a Class B noxious weed in Washington State. Not known to be toxic to pets or humans.

Native Range

Lamiastrum galeobdolon is native to Europe and western Asia, occurring in deciduous woodlands and hedgerows from sea level to approximately 5,000 feet (1,500 m) elevation. The species was introduced to North America as an ornamental ground cover; the variegated cultivars escaped and naturalized in the Pacific Northwest, particularly in urban forests, municipal parks, and riparian areas west of the Cascades, from southern British Columbia through western Washington and Oregon to northern California.

Suggested Uses

Used in noxious weed identification training for Pacific Northwest urban foresters, park managers, and municipal natural-area staff. A primary case study in the garden-escape pathway for invasive species introduction — the species illustrates the gap between legal retail sale and ecological impact that characterizes many Class B and Class C ornamental invasives. Studied in shade-tolerant ground cover invasion ecology, specifically the mat-forming displacement of native herbaceous layers under deciduous tree canopies. The Lamiaceae square stem and two-lipped flower morphology are taught in plant family identification exercises alongside Salvia, Nepeta, and Stachys.

How to Identify

Habit is stoloniferous spreading evergreen ground cover at 8–24 inches (20–60 cm) tall and 24–72 inches (60–180 cm) or more wide via long above-ground stolons. Leaves are opposite, ovate to triangular, 1–3 inches (2.5–8 cm) long, with crenate-serrate margins, in dark green with conspicuous silvery-white variegation splotches (the escaped cultivated forms). Stems are square in cross-section — the Lamiaceae diagnostic trait. Flowers are yellow two-lipped 0.6–0.8 inch (15–20 mm) long in whorls of 4–8 in upper leaf axils in late spring. Stolons run long and arching, rooting at each node. Compared with Lamium purpureum (purple dead-nettle), flowers are yellow rather than purple, the habit is a perennial stoloniferous ground cover rather than an annual, and silver variegation is present rather than absent; compared with Glechoma hederacea (creeping Charlie), flowers are yellow rather than blue-purple, leaf size runs 1–3 inches rather than 0.5–1 inch, and flowering stems are upright rather than creeping with the foliage; compared with native Stachys cooleyae (Cooley's hedgenettle), leaves are silver-variegated rather than uniformly green and habit is stoloniferous rather than rhizomatous with upright stems.

Appearance

Size & Dimensions

Height8" - 2'
Width/Spread2' - 6'

Reaches mature size in approximately 2 years

Colors

Flower Colors

yellow

Foliage Colors

green
silver

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~3 weeks
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SpringSummer
Yellow two-lipped flowers 0.6–0.8 inch (15–20 mm) long in whorls of 4–8 in the upper leaf axils appear from May through June in USDA zones 4–9. Individual whorls bloom over 2–3 weeks. In the Pacific Northwest, peak bloom runs late May through mid-June. The species is pollinated by bumblebees that reach the tubular corolla with their long tongues. Seed production runs limited in the escaped variegated cultivars — the plant's spread is overwhelmingly clonal via stolon extension and fragment regeneration rather than seed.

Detailed Descriptions

Flower Description

Yellow two-lipped 0.6-0.8 inch long with brown markings on the lower lip; whorls of 4-8 flowers in upper leaf axils in late spring

Foliage Description

Dark green with conspicuous silvery-white variegation splotches; ovate to triangular 1-3 inches long; opposite on square stems with crenate-serrate margins

Growing Conditions

Sun Requirements

Partial ShadeFull Shade
Requires 2-6 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)
357912
Soil Types
loamsiltclay
Drainagemoist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

1-2 years

Care & Maintenance

Care Guide

Listed as a Class B noxious weed in Washington State; management focuses on physical removal of all stolon material from the invaded site. Hand-pulling must capture the entire stolon network, as fragments left on moist soil regenerate from intact nodes within 2–4 weeks. Rolling up the mat of stolons and leaves works well in accessible garden and park positions, lifting the entire colonial mat off the soil surface at one time rather than pulling stem by stem. All removed material is bagged and disposed of in landfill; placing pulled stolons on soil allows re-rooting and the plant re-establishes within the growing season. Follow-up monitoring for 2–3 consecutive years is necessary to remove regrowth from missed stolon fragments that were buried below the initial mat surface. In forest understory settings, removal runs labor-intensive because stolons intermingle with native vegetation and cannot be rolled up as a clean mat — the removal is stem by stem under native-plant canopies. Revegetation with native ground covers such as Polystichum munitum (sword fern), Gaultheria shallon (salal), or Asarum caudatum (wild ginger) after removal prevents re-establishment. The species is still widely sold in retail garden centers despite the Class B listing; public education about the invasive potential of variegated forms is a management priority across the Pacific Northwest.

Pruning

No horticultural pruning applies in a weed-management context. Stolons are pulled, rolled, and bagged rather than pruned in place. In garden settings where the plant is being maintained intentionally within a confined bed, trimming the stolons at the edge of the desired area 2–3 times per growing season prevents spread beyond the planned boundaries, though edge containment alone does not stop fragment-driven spread beyond the trimmed margin.

Maintenance Level

high

⚠️ Toxicity Warning

Non-toxic