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Garlic Mustard Draft Outline - 3/3/08

How the plant got here

• Brought by colonists in 1860’s as a culinary herb

Why it has spread here

• No natural enemies (e.g. insects or fungi)
• Each plant produces hundreds of seeds
• Seeds stick to animal fur, shoes of walkers, car tires, etc., and also float downstream or are carried by the wind (most sources say wind isn’t a significant vector ??), to reach new territory
• Can spread by bringing compost, root stock, or transplants from infected areas
• Longevity of viable seeds in the ground—seeds can germinate at least five years after being produced.
• Extremely high density of growth shades out competition
• Inhibits mycorrhizal fungi that native plants, such as trees, require for growth
• High deer populations can facilitate its spread—
  

• White-tail deer rarely feed on it, instead they consume the competing native plants further assisting its spread
• Trampling by browsing deer encourages seed growth by disturbing the soil.

Impact on native ecosystems

• Reduces the diversity of plants growing in forest understory

• This affects innumerable other species that depend on native plants

• Inhibits regeneration of forests—this can have long-term impacts on the ability of forests to provide habitat and beneficial ecosystem functions such as carbon fixation, oxygen production, erosion control, water retention, filtering of pollutants from water and air.

• Can become a “population sink”:

• e.g. some species of butterflies mistakenly lay their eggs on it instead of their usual host, but the larvae die once they hatch.

Proper identification:

• Biennial

• Seedlings appear early spring, form a dense carpet
• Produces a non-flowering rosette first year which overwinters
• Flowers second year

• Flowers when pods are forming and are green and supple
• Seed pods turn brown and dry and drop seed
• Late summer the spent 2^nd year plants coexist with first year plants on the rise

Control principles

• Important to cut or pull before going to seed. Cutting is ineffective unless is done at ground level and at a specific time period (when plant is approaching/just beginning flowering stage).
• For large patches, start at the perimeter and work in, e.g start at the back of the infestation in the forest and move forward (which usually means moving toward the road.)
• Attack isolated infestations as soon as identified, before they spread out of control. This is especially important in areas that are sensitive and/or where control is difficult, such as wetlands.
• All roots should be removed—easiest when ground is wet—to prevent resprouting.
• The cut end of plants can continue growing and go to seed even without roots, so plant cannot be left on the ground, and never should be composted

• “Bag and trash” is best—follow the directions of your municipality for type of bag.

• Burning and/or chemical application has been used by professionals for large infestations.

• Rate of control after burning and herbicides has not always been satisfactory.
• These techniques can be dangerous to work with.
• They can kill “non-target” native plants and make the area vulnerable to new infestations as garlic mustard seedlings do best in disturbed soil.

• Biological control options are being researched, but the challenge is to find something that will kill garlic mustard while also being safe for native plants.

The importance of community education and mobilization for early detection/rapid response—examples of success stories such as Alaska.

Resources for the most current information on control methods