Ecology and Identification of Giant Hogweed and Cow-Parsnip

Nick Page Raincoast Applied Ecology

July 24, 2008

Greater Vancouver Invasive Plant Council Outline

1. Background on taxonomy and biology

2. Identification

3. Patterns of invasion and pppopulation growth

4. Introduction to control methods

5. Landscape-level control strategies

6. Resources

7. Quiz! Carrot Family

• Heracleum species are members of the Carrot family (Apiaceae or Umbelliferae (both are correct)). • Plants in the Carrot family are usually aromatic with hollow stems and sheathing leaf stalks. • It is a large family with about 300 genera and more than 3,000 species. It includes cumin, parsley, carrot, cilantro, dill, caraway, fennel, parsnip, celery, and cow-parsnip. Heracleum Genus

• There are about 70 species of Heracleum, most in Eurasia. We have one native species (cow-parsnip: Heracleum maximum which used to be called Heracleum lanatum). •Theyypp( are monocarpic perennials (flower once after multi ple years of growth). • Often distinguished by their large size. • Have a group of basal (lower or ground) leaves with a central hollow flowering stem. • Have umbel inflorescences (consists of a number of short flower stalks (called pedicels) which spread from a common point) . Umbrella -like; produce many seeds. Pt2Part 2 - Identifi cati on Similarities: Giant Hogweed and Cow-Parsnip

1. Both are large plants with a central flowering stem above a group of basal leaves. Deep carrot-like taproot. 2. Both flower after multiple years of growth. Inflorescence is a largg,e white umbel, often with several smaller side inflorescences. 3. They have similar chemistry and both contain furano- coumarins which cause dermatitis. 4. Found in similar habitats: moist, open areas or open fCforests; riparian zones. Cow-parsnip much less common in urban areas; more common in moist meadows and forest edges. Underside of compound leaf of giant hogweed

Leaflet

Petiole

Shor t secon dary petiole or petiolule Leaf Shape 1

Giant H ogweed Giant H ogweed

Cow-parsnip Cow-parsnip Leaf Shape 2

Giant H ogweed Giant H ogweed

Cow-parsnip Cow-parsnip

Size

10 cm

Giant H ogweed Giant H ogweed

1.8 m

Cow-parsnip Cow-parsnip Giant Hogweed Cow-parsnip Seed Morphology Seed Morphology Seed blunt at end

Both giant hogweed and cow-parsnip have compound leaves composed of several segments or leaflets.

Oil duct length (>3/4 of seed length) Giant hogweed and shape (expanded at ends) Seed narrowed at end

Oil duct length (1/2 – 3/4 of seed length) Cow-parsnip and shape (narrow) Giant H ogweed Giant H ogweed

Cow-parsnip Cow-parsnip Pt3Part 3 – PttPatterns o fIf Invasi on Dispersal

1. Produces 10,000–120,000 seeds per plant. 2. Seeds can be transported by water, air, and by human activities. 3. Long distance dispersal is often purposeful movement of plants or seeds by gardeners. Sometimes by contaminated soil. 4. Once established , dispersal is either by short distance (1-3 m) movement by wind or medium distance (up to 5 km) by water (ditches, streams). 5. Road edges are often dispersal corridors. 6. No indication of bird dispersal. 7. NiNo issues w ithdiith dispersa lfl of vege ttitative propagu les (roo ts or cut stems). Distribution of Giant Hogweed in BC North Vancouver recorded 1920s

French Creek recorded 1920s

Distribution of Giant Hogweed in BC Introduction point in Mahon Park (1920s)

Giant hogweed in the GVRD Populations in the City of North Vancouver (2003) Populations in King County (2004)

Rapid Population Expansion

1973 1991

Gian t Alien, 2005 Pt4Part 4 – CtlMthdControl Methods RtilbltReport available at: www.giant-alien.dk Four control methods

1) Root cutting for small populations (<50 plants) or where herbicide or mowing is not feasible. Repeated treatments needed. 2) Repeated mowing (1 or 2 times per growing season for 1-5 years) 3) Herbicide application (generally glyphosate) early in the growing season (sprayed, wiped, or stem injected). 4) Mulching with geotextile or wood-chips to prevent germination of new plants. Defer restoration planting at a later date.

• Flower removal can be used to prevent dispersal of additional seeds but will not kill the plant. Root cutting Root Cutting and Excavation

City of North Vancouver (Photos by C. MacDonald) Brush-cutting (no root cutting)

3rd Avenue Site, City of Courtenay Cutting (above-ground) and Mulching

30-40 cm of wood chips

Vanier Park, City of Vancouver Pt5Part 5 – LdLandscape L evel lStti Strategies Small populations at the outer edge of population expansion.

Focus site-level management on small populations of giant hogweed before they become widespread. Populations at the upstream end of streams

Target populations in the headwaters of streams first. Large populations that provide the largest number of seeds. Don’t neglect large populations. Part 6 – Resources

Book: Ecology and Management of Giant Hogweed (Heracleum mantegazzianum) (2007)

Manual: The Giant Hogweed: Best Practice Manual

Website: King County Noxious Weeds: Giant Hogweed

Paper: The Biology of Invasive Alien Plants in Canada, Giant Hogweed (Heracleum mantegazzianum)

Website: Petr Pysek (Czech Invasion Ecologist)

Paper: Biological flora of the British Isles. Heracleum mantegazzianum Sommier &Levier.