Skaneateles Conservation Area/Invasive species/Pastinaca sativa

<< State-regulated and other highly invasive plants at the SCA

Pastinaca sativa
wild parsnip

Pastinaca sativa (wild parsnip)

Wild parsnip (Pastinaca sativa) is a biennial or short-lived monocarpic perennial herbaceous plant that has become quite common in disturbed open sites. It has become a concern at the Skaneateles Conservation Area (SCA) not only for its invasive potential and subsequent loss of native habitat, but because of its phototoxicity. Similar to its close relative, giant hogweed (Heracleum mantegazzianum) and several other members of the carrot family (Apiaceae), wild parsnip produces the compound furanocoumarin in its leaves, stems, flowers, and fruits. This chemical, when activated by long-wavelength ultraviolet (UVA) light (sunlight), causes phytophotodermatitis, which is more like a chemical burn than an allergic reaction and may cause localized pain, rash, severe blistering, and discoloration of the skin.

Parsnip was probably introduced to the New World by early European colonists as a garden vegetable that escaped cultivation, and the wild parsnip found at the SCA is the same species as the parsnips planted in vegetable gardens today and are said to be quite edible if harvested correctly. But would-be foragers should take note that the Apiaceae contains some poisonous relatives such as two native Cicuta (water hemlock) species and of course Conium maculatum, the deadly poison hemlock given to Socrates. While not yet identified at the SCA, these poisonous relatives may be present and have similar a appearance to parsnip. Also, low levels of the the phototoxic furanocoumarins are generally found in parsnip root tissue, but higher levels are probably present in the wild type, so it may be wise to prohibit foraging in general at the SCA.

The naturalized (wild) parsnip and the cultivated parsnip are now generally treated as the same species (Pastinaca sativa). Although there are minor morphological differences between wild and cultivated types, wild parsnip will readily cross pollinate with crop varieties. Although large-scale cultivation of parsnips is no longer common in North America, wild parsnip has become a noxious weed.

Observations of Pastinaca sativa (wild parsnip) at the SCA

The following photographs and corresponding iNaturalist observations of Pastinaca sativa were made at or very near the Skaneateles Conservation Area. Click on images to enlarge and read details on Wikimedia Commons or on the "iNat obs" links to view the corresponding observations at iNaturalist.

• Pastinaca sativa, Skaneateles Conservation Area, 14 Jun 2012. iNat obs
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Invasiveness ranking for Pastinaca sativa (Wild parsnip)

The invasivity ranking and need to manage wild parsnip at all appears to have evolved the past 30-some years. The 1987 Nature Conservancy Element Stewardship Abstract for wild parsnip indicated that research "is not considered a priority since parsnip does not invade high quality natural areas." And the 2008-2009 New York State invasiveness rankings didn't appear to even attempt to rank Pastinaca sativa.

Although not ranked by an available 2008-2009 New York State invasiveness assessment, the 2013 Indiana invasiveness ranking using a slightly modified New York State form is High (71/100 = 71%)

Not regulated by New York State law.

The following rankings, based on the 2013 Indiana ranking of wild parsnip, were modified using habitats more typical of Central New York along with more recent references where available.

1. Ecological impact (20/40)

1.1. Impact on Natural Ecosystem Processes and System-Wide Parameters: Influences ecosystem processes to a minor degree (3/10)

• Invades and modifies disturbed open habitats.

• Well-established natural areas, including fields and meadows, are not likely to be invaded by parsnip.

• It can become quite abundant on the edges of open areas and in disturbed patches within otherwise high-quality habitat.

• Very persistent on sites that remain disturbed or bare such as paths, roadsides, and utility rights-of-way.

• Fuel connectivity in solid thistle patches is often insufficient to carry a fire.

1.2. Impact on Natural Community Structure: Significant impact in at least one layer (7/10)

• Once established at the edges, parsnip can spread into adjacent high-quality areas.

• Wild parsnip out-competes other lower-growing herbaceous vegetation by its luxuriant growth and may displace species that are important nectar sources.

• Mature parsnip plants are taller than the native herbs they replace.

1.3. Impact on Natural Community Composition: Influences community composition (3/10)

• In high-quality prairies, aggressive growth by other species sometimes can outcompete and eventually displace the parsnip.

• Decreases species richness and diversity.

1.4. Impact on other species or species groups: Moderate impact (7/10)

• Some people are sensitive to the touch of the leaves and soon develop a rash if their skin contacts the leaves or plant sap in the presence of sunlight.

• A very painful rash can develop that in some people leaves scars that can persist for several months or longer.

• Wild parsnip is most irritating at the time of flowering.

• Topical contact or ingestion of some furanocoumarins, followed by subsequent exposure to UV radiation causes lesions and cell damage in humans and livestock (including birds) as well as various invertebrates, microorganisms, and plants.

• The furanocoumarins in parsnip are known to be toxic to most insects, besides its specialist (Depressaria pastinacella).

• The concentrations of these compounds have been shown to increase with increased UV-B radiation, which is one of the consequences of climate change.

• After accidental introduction of native predator (Depressaria pastinacella), wild parsnip has increased its toxic compound in its evolutionary arms race.

• This allows it to be even less palatable to other species and increase its allelopathic characteristics, which could expand its range.

2. Biological characteristics and dispersal ability (22/25)

2.1. Mode and rate of reproduction: Abundant reproduction with more than 100 viable seeds per plant (4/4)

• Each plant produces hundreds of small yellow flowers which bloom from June to mid-July.

• Flowers are arranged in a loose compound umbel 4–8 inches in diameter.

• 2000 fruits per plant.

• One, both, or neither of the two mericarps in each fruit may contain a seed.

• Seeds mature by early July.

• Plants die after producing seeds but dead stalks will remain standing through the winter

• Wild parsnip is a perennial that exists as a basal rosette for at least one year and then flowers and dies.

• Wild parsnip often flowers and sets seed during its second year, although it may not flower until subsequent years.

• In the growing season, seeds dispersed in late summer and autumn of the previous year are the first to germinate.

• Plants emerging from spring-germinating seeds are better able to survive extended periods of low precipitation during the summer, and low temperatures during the winter.

• The size of a rosette in a given year determines its fate in the following year, and a critical minimum size prior to vernalization (cold period) is required to initiate flowering.

• If rosettes do not reach the critical minimum biomass flowering may be delayed for one or more years until sufficient reserves have accumulated to support the reproductive growth phase.

2.2 Innate potential for long-distance dispersal: Numerous opportunities for long-distance dispersal (4/4)

• Deer, birds, and small mammals may consume the seeds and disperse them.

2.3. Potential to be spread by human activities: High (3/3)

• Intentional: The seeds are dispersed when the shoots are cut by mowing. Food/Medicine.

• Unintentional: Bird Animal Vehicles/Human Wind Water Other

2.4. Characteristics that increase competitive advantage: Two or more characteristics increase competitive advantage (6/6)

• Wild parsnip poses a severe threat to native plants and humans.

• This plant readily moves into disturbed habitats and along road edges.

• Once populations build, they can spread rapidly and quickly displace native vegetation.

• From roadsides its can spread into woodland openings, meadows, and drainages.

• The ability for this plant to encroach on a wide range of habitats can have profound impacts on sensitive areas.

• It endures a wide range of edaphic conditions, usually dry to mesic soils, but occasionally will be found in wet meadows.

• Grows best on calcareous, alkaline soils and does not tolerate shade well.

• Can be a problem weed in mesic meadow communities.

2.5. Growth vigor: Forms a dense layer above shorter vegetation (2/2)

• Forms dense populations.

2.6. Germination/Regeneration: Can germinate/regenerate in existing vegetation in a wide range of conditions (3/3)

• A range of soil conditions are suitable for wild parsnip, including dry to mesic soils, as well as in wet meadows and ditches.

• Grows best on calcareous, alkaline soils.

• Well-established habitats are not likely to be invaded by parsnip, but it can become quite abundant on edges and in disturbed patches within otherwise high quality sites.

• Highly persistent on sites that remain disturbed or bare such as rocky areas, paths, or roadsides.

2.7. Other species in the genus invasive in New York or elsewhere: (0/3)

• No other species of Pastinaca are known to have naturalized in New York.

• Pastinaca sativa includes both wild and cultivated types of parsnip.

• Cultivated varieties of Pastinaca sativa have probably been planted in the region and could easily escape and cross-pollinate with wild parsnip, which could conceivably alter traits of the wild-type.

3. Ecological amplitude and distribution (21/25)

3.1. Density of stands in natural areas in the northeastern USA and eastern Canada: Large dense stands present in areas with numerous invasive species already present or disturbed landscapes (2/4)

• Large dense stands are present throughout Central New York and more specifically in the Town of Skaneateles, along roadsides and disturbed sites, including within the SCA.

• Not common in pristine areas.

3.2. Number of habitats the species may invade: Known to occur in ≥ 4 listed habitats with ≥ 3 natural (4/6)

• Ditches (managed wetland)
• Cultivated (managed upland)
• Grasslands/old fields (natural upland)
• Shrublands (natural upland)
• Forests/woodlands (natural upland)
• Roadsides (managed upland)

3.3. Role of disturbance in establishment: Can establish independent of any known natural or anthropogenic disturbances (4.4)

• Invades disturbed bare areas.

• Well-established sites are not likely to be invaded, but it can become quite abundant on edges and in disturbed patches within otherwise high quality habitat.

• Highly persistent on sites that remain disturbed or bare such as rocky areas, paths, or roadsides.

• Can invade natural areas with fertile soil.

3.4. Climate in native range: Native range includes climates similar to those in Central New York (3/3)

• Primarily a plant of temperate regions.

• Invasive throughout much of the globe.

3.5. Current introduced distribution in the northeastern USA and eastern Canada: Present as a non-native in >8 northeastern USA states and/or eastern Canadian provinces and/or categorized as a problem weed (e.g., “Noxious” or “Invasive”) in 2 northeastern states or eastern Canadian provinces (4/4)

• Canada: present in all provinces and territories except Nunavut.
• United States: present in all states except Hawaii, Mississippi, Alabama, Georgia, and Florida.
• Listed as invasive in: Alaska, Indiana, Kentucky, Minnesota, Ohio, Pennsylvania, West Virginia, and Wisconsin

3.6. Current introduced distribution of the species in natural areas in the 8 NY PRISMs: Present in all PRISMS (4/4)

• Present in the Finger Lakes PRISM.

4. Difficulty of control (6/10)

4.1. Seed banks: Seeds (or vegetative propagules) remain viable in soil for at least 1 to 10 years (2/3)

• Seed can remain viable in the soil for up to four years.

4.2. Vegetative regeneration: Regrowth from ground-level meristems (1/3)

• Mowing when the primary umbel begins flowering (May to June) may be most effective at reducing fruit production because the considerable biomass allocation to stem production reduces reserves available for flower and seed production.

4.3. Level of effort required: Management requires a major short-term investment. Eradication is difficult (3/4)

• Although eradication is desirable from a human safety and ecological standpoint, in some situations the best control measure is to do nothing.

• In high-quality meadows, aggressive growth by other species sometimes can outcompete and eventually displace the parsnip.

Mechanical Control:

• The best control is achieved mainly through hand-pulling.

• Plants should be pulled and removed so that seeds do not develop, and plants do not resprout.

• Another effective practice involves cutting the plant below the root crown before seed set during spring of the second year.

• Mowing probably favors parsnip maturation by allowing more sunlight to reach immature parsnip plants, which are too low to be damaged by the mower.

• Mowing also reduces the density, height, and flowering of other species that are potentially good competitors against parsnip, such as common goldenrod.

Prescribed Fire:

• Burning does not successfully control parsnip because it removes litter and taller plants, providing favor-able conditions for parsnip rosettes to develop.

• Periodic burning maintains the vigor of native plants, allowing them to compete with parsnip.

Biocontrol:

• The parsnip webworm damages some individual plants severely but is not known to eradicate whole patches and is not likely to be useful as a biocontrol agent.

Chemical Control:

• If mechanical methods have failed to control wild parsnip or are not feasible, a 2% spot application of glyphosate to basal rosettes is a recommended treatment.

• Apply glyphosate to individual plants with a hand sprayer in late fall after most native vegetation is dormant.

• Late fall application minimizes the potential harm to non-target species.

• It may be necessary to treat the same area again annually until missed plants and plants originating from the seed bank are eliminated.

• Chemical controls are effective but should be used sparingly on quality natural areas.

• The best method is to burn the site, then follow with spot application of 1-3% glyphosate.

• Immediately after a burn, wild parsnip is one of the first plants to green.

• Glyphosate can be spot applied to the basal rosette of the parsnip with little effect on dormant species.

• Management can be difficult and does require follow up treatment in edge habitats and conservation plantings.