Himalayan balsam

(Impatiens glandulifera)

 

Invasive implications

Himalayan balsam is a bamboo-like annual with characteristic flowers resembling the shape of an English “Policeman’s helmet” (one of its common names). It is native to the Western Himalaya, most likely brought to Canada in the early 1900’s as an ornamental. This plant is extremely invasive to moist, natural areas and is swiftly spreading through the watercourses of the Lower Mainland. Himalayan Balsam can grow to three meters, which combined with its high reproductive output and rapid growth enables this weed to dominate local vegetation. Additionally, after dying back in the fall, it exposes bare riverbanks resulting in increased erosion during high winter flows. Himalayan balsam has a poor root structure so it is relatively easy to pull by hand. Controlling this plant, like many invasives, requires stringent and long term efforts to be effective. Himalayan balsam is easily identifiable with its whorled leaves (usually in threes) and recognizable stalk as shown below.

 

Identification

Spring

Summer

Winter

  •  stem is pink-red to green

  •  grows up to 3m in height
  •  stalks die back and rot, turning pale 

Leaf

Stem

Flower/Seed pods

 

 

 

  •  shiny and dark green
  •  long, slender with serrate edges
  •  reddish midrib
  •  up to 15cm long
  •  opposite or in whorls of 3, symmetrical
  •  green, vertical grooves
  •  hollow and jointed
  •  sometimes branched
  •  sappy and brittle
  •  leaves and side branches arise  from stem joints
  •  purplish pink to pale pink, rarely white
  •  slipper or policeman's helmet shape
  •  carried on long stalks
  •  appear June to October
  •  seeds are 4-7mm diameter, white to dark brown/black (4-16/pod)

 

 

Key Features

Himalayan balsam does not have rhizomes per se; however, cut stems do re-grow from the roots. This weed has explosive seed pods that catapult up to 2500 seeds for each plant, travelling over ten kilometers before germinating in spring. Merely touching the pods when they are ready to burst demonstrates this intriguing phenomenon. The buoyant seeds usually follow watercourses or are spread by human interactions. Seeds are transported near the channel bottom and are deposited on river banks only during heavy floods. Compared to many native plants, this weed offers a rewarding supply of nectar to pollinators thus adding to its invasiveness. Himalayan balsam is partially shade tolerant and located in lowland, riparian areas including stream sides, ditches, and wetlands. It is also quite common in private gardens where it often invades to such an extent that it becomes a real nuisance instead of a garden beauty.

  

 

Control Measures

Since Himalayan balsam primarily spreads through waterways, an upstream strategy is strongly recommended. This method attempts to limit the impact of dispersal along rivers by tackling upstream populations first thereby reducing the ability of the species to expand downstream.  Mechanical control such as mowing and uprooting is the method of choice for Impatiens glandulifera since it is an annual with relatively weak roots. Work should be completed before the fruits of the plant begin to ripen. This control may need to extend over two years as seeds often remain viable for more than one year. It is important to realize that control is ineffective if the sources of seeds are not simultaneously suppressed.

So far there are no known 'safe' biological agents. Additionally, chemical control is not recommended as a control option because mechanical control is generally feasible and this plant is often interspersed between native plants as opposed to complete monocultures with very low nature conservation value. Lastly, it is very important to exercise extremely effective control efficiency with Himalayan Balsam due to the pervasiveness of this invasive plant.

 

Non Chemical Control

  Hand pulling Cutting Grazing
How Pull plant out using hands or digging tool if necessary Cut at ground level using, for example, a machete or scythe By cattle and sheep
When Before the plant flowers and sets seed Before the plant flowers and sets seed From early spring throughout the growing season
Duration

 

Annually, until no new seedlings appear Annually, until no new seedlings appear Intensive grazing may be necessary until no new seedlings appear
Pros/Cons Cost effective but labour intensive Cost effective but labour intensive Efficient control; may do more environmental damage, especially in sensitive riparian habitats

 

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

 

Additional Resources