yellow archangel

(Lamiastrum galeobdolon)

 

 

Invasive implications

This groundcover is native to Europe and Asia, probably introduced to North America for ornamental use. There are many subspecies of Lamiastrum galeobdolon including argentatum, flavidum, montanum. These subspecies can also have variations, accounting for subtle differences between each cultivar. The following information sheet portrays pictures of the subspecies montanum variation 'variegatum', a common species in the Lower Mainland. The invasiveness of yellow archangel subspecies vary, yet most are extremely vigorous and can grow in an array of environmental conditions and habitats. Yellow archangel has overtaken large wooded areas in the Pacific Northwest, preferring partial shade environments although growing just about anywhere. In most cases, it is a garden escapee, spreading to nearby parks and other wooded or open areas. As an evergreen vine, Lamiastrum galeobdolon can swiftly displace local native groundcovers such as sword fern, trillium, and false-lily-of-the-valley. This weed is often mistaken for Lamium species, but has its own genus because it has yellow flowers and minor differences in floral structure from the Lamium species. Fortunately, yellow archangel is easy to pull out, making control efforts both tolerable and worthwhile.

 

Identification

Spring

Summer

                      Winter

  •  often grows over 1 m in first growing season

 
  •  more erect in sun than shade
  •  may advance at rate of 1m/year
  •  optimum growth at 22o C
  •   depending on climate, it may totally defoliate or keep some of its leaves during winter. (Lamiastrum galeobdolon ssp. argentatum)

Leaves

Stem/Roots

Flower/Fruit
 

 
  •  smooth serrated edges, silver/white markings with green trim
  •  shade leaves are larger, thinner and darker green than sun leaves
  •  undersides are lighter green
  •  stems are green, square, and hairy - especially at base of stem
  •  roots of mature plants exceed 30cm in length and reach a depth of over 20cm
  •  runner-like side shoots
  •  yellow with hooded upper petal and lipped lower petal (helmet-shaped)
  •  blooms in April and May for short periods (approximately 7 days)
  •  clusters of small flowers occur at the ends of stems

 

Similar Plants

Is similar to Lamiastrum galeobdolon variation 'Herman's Pride', which differs in being a clump perennial instead of growing as a vine groundcover. Hermans Pride has pointed leaves, is heavily veined with metallic silver, and does not tend to spread. We are not certain whether this occurs locally.

Key Features

Yellow archangel occurs on a wide range of soil types, including varying pH, organic content, and drainage conditions. It can grow on soils that are waterlogged in winter and is also often found in damp woods, banks and woodland margins. This weed does not develop in particularly dry soils or in full sun conditions. It is said to be a medium-sized, semi-evergreen herb, notable for growing very well on forest floors with deep leaf litter. Interestingly, yellow archangel can be severely damaged by trampling, which is considered the primary reason it seldom occurs away from woodlands and hedgerows in the British Isles. Most subspecies can withstand heavy frost, normally without loss of leaves.

Seedlings of yellow archangel rapidly develop into erect young plants (initially), which root at the nodes. Propagation occurs by both seeds and vegetatively from stolons. Flowers have reddish-brown markings that act as nectar guides on the lower lip of the petal. This lower lip serves as a platform for large insects. Flowers bloom for short periods and can self-pollinate if pollination does not occur via insects. Seeds are primarily dispersed by ants, which are attracted to specific oils within the seed . These ants have been observed to transport seeds up to 70 meters! Seeds (around 800 per plant) appear in late spring and germinate best when exposed to cool wet conditions for approximately six months.

 

Control Measures

To date, there is limited information on control practices for yellow archangel. Since this vine does not have a deep rooting system, it can be pulled out by hand. Chemical control is another option but may not be practicable due to the fact that Lamiastrum galeobdolon is often interspersed with native plants. It is advisable to commence control efforts by containing existing stands along with preventing further establishment of new stands as these plants are usually found in 'pockets'.

 

Non Chemical Control

Chemical Control
  Hand pulling/Cutting Foliar Application
How Vines can be pulled out by hand with relative ease. Rooted portions of vines will remain alive and should be pulled, and repeatedly cut Apply a 2.5% mixture of triclopyr amine in water to the leaves or cut first, allow to re-grow and apply the same mix to new foliage. Herbicide will be absorbed through the stem bark for additional effect
When Fall to early spring, before seed sets

Summer to fall, as long as temperatures are above 12o C. In areas where native plants are interspersed, apply prior to emergence of these species or delay until they have died back
Duration

 

 Efforts must be long term until stands are eradicated - may take several years dependent on size of area and intensity of efforts. Repeat herbicidal treatments are likely necessary, follow-up monitoring should be conducted to evaluate the success of treatments
Pros/Cons Safe and effective method but labour intensive Effective and less laborious than hand pulling. See chemical warning below

 

Control Warnings:

Disposal - Make sure to properly discard all plant pieces in thick plastic bags and transport them to a sanitary landfill site or incinerator. Composting is not an appropriate means of disposal as this may result in further distribution. Remember that humans can actually spread invasive plants by taking seeds from one place to another on clothing, tires, equipment, etc.

Chemicals - Although some chemicals are approved for control of invasive plants, extreme caution must be taken as many pesticides are harmful to humans. Permits may be required for chemical use and buffer zones exist beside waterways to protect fish and wildlife. Chemical control is not a long-term solution and therefore should be part of a finite plan and applied sparingly. Please see the following web sites for further information: Provincial: MWLAP Pest Information  Federal: Pest Management Regulatory Agency

Biological - Extreme caution must be taken when introducing one organism to control another. Intensive testing must occur before initiating a safe and effective biological control agent. Please contact local government or environmental agencies to determine available volunteer opportunities.

 

Additional Resources