Yellow Archangel

General

As with many plants grown for agricultural or horticultural purposes, there are several subspecies and cultivars of yellow archangel, because most subspecies share many invasive characteristics; yellow archangel is inclusive of all its subspecies and cultivars.
Popular choice for ground coverage, especially in shady areas, this plant is also used in hanging baskets and flowerbeds because of its silvery foliage.
Native to temperate regions of Asia and Europe.

Identification

Semi-evergreen to perennial, fast growing, viny, herbaceous plant that grows prostrate to the ground, forming a dense ground cover and also climbing up and over low-growing vegetation and small structures such as tree stumps.
In bright sun, the plant will grow more erect and leaves are typically thicker, brighter and larger than shade leaves.
Leaves are oppositely arranged on a purplish, square-shaped, hairy stem.
Leaves are serrated and ovate shaped, with rounded or cordate bases.
Leaf undersides are often lighter green or sometimes purple.
Leaf upper sides often are variegated with silver or white pattern.
Bright yellow flowers, tubular-campellate (long, bell-shape), with an upper and lower lip.
The flowers are produced as pairs of dense clusters internodally (between pairs of leaves) on flowering stems between April and June.
The plant contains ethereal oils in its leaves, giving it a distinctive odor described as unpleasant and yet not revolting.

Photos

Habitat

Dense mats can spread over other plants including sword fern, Trillium, and False lily-of-the-valley in woodlands of the Pacific Northwest.
Tolerates a wide range of soil, water, and shade conditions.
Typically restricted to woodlands, stream banks and hedgerows.
Grows on a variety of substrates including limestones, clays, sandstones, conglomerates, recent alluvia and deep loamy soils rich in nutrients.
Can tolerate waterlogged, damp, and dry soil, although it cannot persist in permanently flooded areas.
Shade tolerant but thrives in wooded areas that are only lightly shaded.
The plant grows back heavily and can become dominant after coppicing (cutting back to base).

Reproduction and Spread

Flower and seed production is typically greater during hot, dry summers; whereas stoloniferous reproduction is more prevalent during wet, cool ones.
Average seed production by a single plant is approximately 800 seeds.
Vegetation propagation occurs through stoloniferous plant production as well as through plant fragmentation. When a stem breaks or a portion decays, the resulting fragments grow as individual plants with adventitious root development occurring between leaf nodes.
The sources of many of the escaped populations occurring in natural areas in the county appear to be compost piles and improperly discarded yard waste.

Mechanical Control

Viny plants are easily pulled out by hand during the fall through early spring; however, great care must be taken to remove all parts of plant, as rooted fragments will regenerate.

Chemical Control

Best time to apply herbicide, at least in British Columbia, is between summer and fall, when temperatures are higher than 54 degrees Fahrenheit
Apply to actively growing foliage
Herbicides include
- Glyphosate
- Imazapyr
- Triclopyr