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Quiz: Invasive Species Identification

Test your ability to identify Minnesota's most damaging invasive species and understand their ecological impacts.

1. What is the single most reliable field identification feature for Garlic Mustard?

  1. Its bright purple flowers in summer
  2. The distinctive garlic or onion odor when leaves and stems are crushed
  3. Its thorny stems and red berries
  4. The milky white sap that oozes when stems are broken
Show Answer

The correct answer is B. Crushing Garlic Mustard leaves or stems produces a distinctive garlic or onion smell that is the single most reliable identification feature. Garlic Mustard is a biennial with kidney-shaped leaves in the first year and triangular toothed leaves with small white four-petaled flowers in the second year. It does not have thorns, colored berries, or milky sap — those features belong to other invasive species.

Concept Tested: Garlic Mustard

See: Chapter 8

2. How can you tell Common Buckthorn apart from Glossy Buckthorn in the field?

  1. Common Buckthorn grows near water; Glossy Buckthorn grows in dry prairies
  2. Common Buckthorn has toothed leaves, sub-opposite arrangement, and thorns; Glossy has smooth-edged leaves, alternate arrangement, and no thorns
  3. Common Buckthorn has red berries; Glossy Buckthorn has black berries
  4. Common Buckthorn is a vine; Glossy Buckthorn is a tree
Show Answer

The correct answer is B. Common Buckthorn has finely toothed leaf margins, sub-opposite leaf arrangement, and small sharp thorns at twig tips. Glossy Buckthorn has smooth (untoothed) leaf margins, alternate leaf arrangement, and no thorns. Both species have dark berries and yellow-orange inner bark when scraped. Glossy Buckthorn tends to prefer wetter habitats like bogs and fens, while Common Buckthorn invades upland woodlands.

Concept Tested: Common Buckthorn / Glossy Buckthorn

See: Chapter 8

3. Why is Wild Parsnip considered a direct threat to human health, unlike most other invasive plants?

  1. Its pollen causes severe respiratory allergies
  2. Its roots contaminate drinking water supplies
  3. Its sap contains furanocoumarins that cause severe burns and blisters when skin contacts the sap and is then exposed to sunlight
  4. Its seeds are toxic if accidentally ingested
Show Answer

The correct answer is C. Wild Parsnip sap contains chemicals called furanocoumarins that cause phytophotodermatitis — severe burns and blisters when the sap contacts skin and is then exposed to sunlight. This makes Wild Parsnip a direct health hazard for outdoor recreation and land management. Always wear long sleeves, gloves, and eye protection when working near Wild Parsnip. If sap contacts skin, wash immediately and avoid sun exposure.

Concept Tested: Wild Parsnip

See: Chapter 8

4. Why are European Earthworms considered invasive in Minnesota's northern forests, even though most people think of earthworms as beneficial?

  1. They eat the seeds of native wildflowers, preventing reproduction
  2. They consume the leaf litter duff layer that native plants need to germinate and grow, fundamentally changing forest soil
  3. They attract invasive bird species that compete with native songbirds
  4. They carry diseases that kill native tree species
Show Answer

The correct answer is B. Minnesota's northern forests evolved without earthworms after glaciers eliminated native species roughly 10,000 years ago. The thick duff layer of decomposing leaves is essential habitat for native plants, insects, and salamanders. European earthworms, introduced through fishing bait and landscaping soil, rapidly consume this duff layer, leaving bare mineral soil. This causes dramatic declines in native plant diversity, including Trillium, Wild Ginger, and Solomon's Seal.

Concept Tested: European Earthworms

See: Chapter 8

5. What field sign is the most reliable indicator of Emerald Ash Borer infestation in an ash tree?

  1. Yellow leaves in summer
  2. Mushrooms growing at the base of the trunk
  3. Small, D-shaped exit holes in the bark where adult beetles emerged
  4. Bark turning white and peeling off in sheets
Show Answer

The correct answer is C. The most reliable field sign for Emerald Ash Borer is the distinctive small, D-shaped exit holes (about 1/8 inch wide) in ash tree bark where adult beetles have emerged. Other signs include S-shaped galleries under the bark, vertical bark splitting, canopy dieback starting from the top, new sprouts growing from the trunk, and increased woodpecker activity. EAB has been confirmed in dozens of Minnesota counties and threatens an estimated one billion ash trees statewide.

Concept Tested: Emerald Ash Borer

See: Chapter 8

6. A mature Purple Loosestrife plant can produce how many seeds per year?

  1. About 500
  2. About 10,000
  3. Over two million
  4. About 100,000
Show Answer

The correct answer is C. A single mature Purple Loosestrife plant can produce over two million seeds per year, which is why it can rapidly dominate wetlands. Purple Loosestrife forms dense stands that replace native cattails, sedges, and wetland wildflowers, destroying nesting habitat for waterfowl and marsh birds. Biological control using specialized Galerucella leaf-feeding beetles has been partially successful in Minnesota, but the species remains a serious wetland invader.

Concept Tested: Purple Loosestrife

See: Chapter 8

7. What makes Reed Canary Grass one of the most difficult invasive species to control in Minnesota wetlands?

  1. It produces toxic chemicals that prevent all other plants from growing
  2. It grows only underwater where removal equipment cannot reach
  3. It spreads aggressively by thick rhizomes, forms impenetrable monocultures, and recolonizes faster than native plantings can establish
  4. It is protected by Minnesota law and cannot legally be removed
Show Answer

The correct answer is C. Reed Canary Grass spreads by thick horizontal rhizomes to form dense, impenetrable monocultures that exclude nearly all other vegetation. Its dense root mat prevents native seeds from reaching soil. Wetland restorations frequently fail because Reed Canary Grass recolonizes faster than native plantings can establish. It tolerates both standing water and dry periods, making it extremely adaptable. It is one of Minnesota's most persistent wetland invaders.

Concept Tested: Reed Canary Grass

See: Chapter 8

8. You are surveying a woodland in October and notice one shrub species that still has bright green leaves while all native trees and shrubs have dropped theirs. What invasive species should you suspect?

  1. Garlic Mustard
  2. Wild Parsnip
  3. Common Buckthorn
  4. Spotted Knapweed
Show Answer

The correct answer is C. Common Buckthorn has an extended growing season, leafing out before native plants in spring and holding green leaves well into late fall after native species have gone dormant. This late leaf retention is a key seasonal identification clue and also gives Buckthorn a competitive advantage — it captures sunlight for weeks longer than native plants. Fall is actually one of the easiest times to spot Buckthorn because its green foliage stands out against bare native branches.

Concept Tested: Common Buckthorn

See: Chapter 8

9. Which trait do many successful invasive species share that gives them a competitive advantage over native plants?

  1. They require pollination by native bees to reproduce
  2. They can only grow in undisturbed, high-quality habitat
  3. They arrive without the natural enemies that controlled them in their home range
  4. They require mycorrhizal fungal partnerships to absorb nutrients
Show Answer

The correct answer is C. Invasive species succeed because they arrive in a new environment without the insects, diseases, and herbivores that controlled their populations in their native range. Freed from these natural checks, they can grow and reproduce unchecked. Many also share additional competitive traits: early leaf-out, late leaf retention, prolific seed production, rapid growth rates, allelopathy, and tolerance of disturbed soils.

Concept Tested: Invasive Species Impact

See: Chapter 8

10. Japanese Barberry has been linked to an unexpected public health concern beyond its ecological damage. What is it?

  1. It produces allergenic pollen that worsens asthma
  2. Its dense growth creates humid microhabitats that increase blacklegged tick (deer tick) populations
  3. Its berries are poisonous to children and pets
  4. It releases chemicals that contaminate well water
Show Answer

The correct answer is B. Research has shown that Japanese Barberry's dense, mounded growth creates humid microhabitats that favor blacklegged ticks (deer ticks), potentially increasing the risk of tick-borne diseases like Lyme disease. Studies in the eastern United States found significantly higher tick densities in forests with barberry-infested understories compared to forests with native shrubs. This public health connection adds urgency to efforts to remove Japanese Barberry from Minnesota woodlands.

Concept Tested: Japanese Barberry

See: Chapter 8

Ready to use these ideas rather than recall them? Try the Applied Quiz for this chapter — ten scenario questions that put you in a situation and ask what to do.